Experimental - Spectroscopy
Experimental - Spectroscopy
Experimental - Spectroscopy
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®<br />
June 2011 Volume 26 Number 6<br />
www.spectroscopyonline.com<br />
FT-IR Analysis of<br />
Algae for Biofuels<br />
Maxwell’s Equations<br />
Classical Least Squares<br />
and Spectral Results<br />
SERS Analysis of<br />
Methyl Yellow in<br />
Silver Colloid
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4 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
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6 <strong>Spectroscopy</strong> 26(6) June 2011<br />
June 2011<br />
Volume 26 Number 6<br />
®<br />
CONTENTS<br />
Columns<br />
THE BASELINE<br />
Maxwell’s Equations, Part II<br />
www.spectroscopyonline.com<br />
Volume 26 Number 6<br />
JUNE 2011<br />
14<br />
In the realm of classical physics, Maxwell’s equations still rule, just as Newton’s equations of<br />
motion rule under normal conditions.<br />
David W. Ball<br />
CHEMOMETRICS IN SPECTROSCOPY<br />
22<br />
Classical Least Squares, Part VI: Spectral Results<br />
The detailed examination of the spectral behavior of three-component mixtures continues.<br />
Howard Mark and Jerome Workman, Jr.<br />
Cover image courtesy of<br />
Getty Images.<br />
ON THE WEB<br />
PITTCON THEATER<br />
<strong>Spectroscopy</strong> and LCGC presented LIVE<br />
video interviews at Pittcon 2011. Interviews<br />
with leading experts covered trends and<br />
applications in ICP/ICP–MS and hyphenated<br />
techniques.<br />
Specific topics include:<br />
ICP-MS in the Clinical Laboratory<br />
Deanna Jones, Research Chemist,<br />
Centers for Disease Control and Prevention<br />
Using LC–MS with Online Sample<br />
Preparation to Survey Metabolites<br />
Formed In Vitro<br />
Samuel Yang, University of Texas, Arlington<br />
Multidimensional Chromatography–<br />
MS in Polymer Analysis<br />
Hernan Cortes, Hernan J. Cortes Consulting<br />
Articles<br />
Optimizing FT-IR Sampling for a Method to 30<br />
Determine the Chemical Composition of Microbial Materials<br />
Algae and other aquatic species are promising sources for biomass that can be<br />
economically converted into fuel, and several infrared sampling techniques can be<br />
used to analyze these samples.<br />
Steve Lowry<br />
The pH Dependence of the SERS 38<br />
Spectra of Methyl Yellow in Silver Colloid<br />
Surface plasmon resonance, charge-transfer resonance, and their combination determine<br />
the enhancement of surface-enhanced Raman scattering signals, and the varying intensities<br />
of the signal at different pH levels may result from the change in contributions of the<br />
combined system.<br />
Zhen Long Zhang, Da Hu Chang, and Yu Jun Mo<br />
Watch the interviews online at:<br />
www.spectroscopyonline.com<br />
SPECTROSCOPY WAVELENGTH<br />
Subscribe to our monthly newsletter, which<br />
features interviews, technology roundtables,<br />
new products, and more.<br />
June Interview: Can LIBS help Japan<br />
with the nuclear crisis?<br />
Join the<br />
<strong>Spectroscopy</strong> Group<br />
on LinkedIn<br />
DEPARTMENTS<br />
News Spectrum . . . . . . 10<br />
Product Resources . . . . 44<br />
Calendar . . . . . . . . . . . . 48<br />
Short Courses . . . . . . . 49<br />
Ad Index . . . . . . . . . . . . 50<br />
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www.spectroscopyonline.com June 2011 <strong>Spectroscopy</strong> 26(6) 9<br />
Editorial Advisory Board<br />
Ramon M. Barnes University of Massachusetts<br />
Paul N. Bourassa Unity Home Medical<br />
Chris W. Brown University of Rhode Island<br />
Kenneth L. Busch Wyvern Associates<br />
Ashok L. Cholli University of Massachusetts at Lowell<br />
David M. Coleman Wayne State University<br />
Bruce Hudson Syracuse University<br />
David Lankin University of Illinois at Chicago, College of Pharmacy<br />
Barbara S. Larsen DuPont Central Research and Development<br />
Ian R. Lewis Kaiser Optical Systems<br />
Jeffrey Hirsch Thermo Fisher Scientific<br />
Howard Mark Mark Electronics<br />
R.D. McDowall McDowall Consulting<br />
Gary McGeorge Bristol-Myers Squibb<br />
Linda Baine McGown Rensselaer Polytechnic Institute<br />
Robert G. Messerschmidt Rare Light, Inc.<br />
Francis M. Mirabella Jr. Mirabella Practical Consulting Solutions, Inc.<br />
John Monti Shimadzu Scientific Instruments<br />
Thomas M. Niemczyk University of New Mexico<br />
Anthony J. Nip CambridgeSoft Corp.<br />
John W. Olesik The Ohio State University<br />
Richard J. Saykally University of California, Berkeley<br />
Jerome Workman Jr. Unity Scientific<br />
Contributing Editors:<br />
Fran Adar Horiba Jobin Yvon<br />
David W. Ball Cleveland State University<br />
Kenneth L. Busch Wyvern Associates<br />
John Coates Coates Consulting<br />
Howard Mark Mark Electronics<br />
Volker Thomsen Consultant<br />
Jerome Workman Jr. Consultant<br />
Process Analysis Advisory Panel:<br />
James M. Brown Exxon Research and Engineering Company<br />
Bruce Buchanan Sensors-2-Information<br />
Lloyd W. Burgess CPAC, University of Washington<br />
James Rydzak Glaxo SmithKline<br />
Robert E. Sherman CIRCOR Instrumentation Technologies<br />
John Steichen DuPont Central Research and Development<br />
D. Warren Vidrine Vidrine Consulting<br />
European Regional Editors:<br />
John M. Chalmers VSConsulting, United Kingdom<br />
David A.C. Compton Industrial Chemicals Ltd.<br />
<strong>Spectroscopy</strong>’s Editorial Advisory Board is a group of distinguished individuals<br />
assembled to help the publication fulfill its editorial mission to promote the effective<br />
use of spectroscopic technology as a practical research and measurement tool.<br />
With recognized expertise in a wide range of technique and application areas, board<br />
members perform a range of functions, such as reviewing manuscripts, suggesting<br />
authors and topics for coverage, and providing the editor with general direction and<br />
feedback. We are indebted to these scientists for their contributions to the publication<br />
and to the spectroscopy community as a whole.<br />
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10 <strong>Spectroscopy</strong> 26(6) June 2011<br />
News Spectrum<br />
New Forensic Laser Technique<br />
Locks Hair in Time<br />
Jim Moran, a geochemist at the Pacific Northwest<br />
National Laboratory (Richland, Washington), led a team of<br />
researchers in the development of a new laser-powered<br />
chemical analysis technique that can take dozens of<br />
samples from a single strand of hair and distinguish the<br />
chemical signatures of each.<br />
Because existing methods destroy small samples, they<br />
don’t allow for exact time-based measurements. Using the<br />
new technique, which breaks up material instead of scorching<br />
it, carbon isotope measurements from human hair can be<br />
taken over time, revealing information about what people ate,<br />
whether they’ve traveled, and where they’ve been.<br />
The technique is described in detail in a paper published<br />
by Moran and his team in the April 12 issue of Rapid<br />
Communications in Mass Spectrometry.<br />
“The carbon you eat goes into your hair, so hair is a<br />
record of carbon ratios. If you’ve been traveling, I could<br />
guess which countries you’ve been to or what you<br />
ate,” Moran said in a Wired online article, indicating<br />
that forensic scientists should find the technique<br />
useful. Biologists exploring food pathways in microbes,<br />
and paleontologists using carbon-based data to look<br />
at ancient environments may also find value in the<br />
technique.<br />
www.spectroscopyonline.com<br />
In addition to carbon sampling, the laser-ablation<br />
system may also work with other chemical isotopes,<br />
including nitrogen, oxygen, and sulfur as Moran’s team is<br />
working on developing those applications.<br />
Research Funding Finds Friends<br />
in Gingrich, Bernanke<br />
In today’s difficult economic times, Americans may<br />
be surprised to hear former speaker of the House and<br />
potential Republican presidential candidate Newt Gingrich<br />
argue for increased spending on medical and scientific<br />
research. In doing so, he contradicts fellow GOP leader,<br />
Paul Ryan, chairman of the House Budget Committee,<br />
who would cut spending in these areas.<br />
According to a Wall Street Journal article, Gingrich, whose<br />
mother was bipolar, is a strong supporter of brain research.<br />
At a Brookings Institution conference on April 22, he said that<br />
while he applauds Ryan’s “courageous effort” to “right-size”<br />
government, he disagrees with some of the details.<br />
“One of them is cutting investment in science and research,”<br />
Gingrich said at the conference. “It’s essentially like saying<br />
I want to save money on your car (so) we’re not going to<br />
change the oil. And for about a year I can get away with it, then<br />
the engine will freeze, and we have to change the engine.”<br />
President Obama, in his Plan for Science and Innovation,<br />
issued in February, called for doubling the budgets of<br />
Market Profile: Process FT-NIR for PAT in Pharma and Biopharma<br />
Fourier-transform near-infrared (FT-NIR)<br />
spectroscopy continues to be a rapidly growing<br />
process analytical technique, particularly in<br />
the pharmaceutical and biopharmaceutical industry.<br />
The technique offers a number of advantages<br />
for online applications, and most of the major<br />
NIR instrument vendors now compete in this<br />
segment of the market.<br />
FT-NIR spectrometers make<br />
use of a simpler mechanical<br />
design than dispersive NIR<br />
instruments, and therefore<br />
provide a more rugged<br />
and reliable design that is<br />
advantageous in any industrial<br />
setting, including pharmaceutical<br />
and biopharmaceutical<br />
manufacturing. In addition,<br />
7%<br />
5% 5%<br />
7%<br />
14%<br />
20%<br />
FT-NIR provides simultaneous analysis<br />
of all frequencies in the spectrum range, rather<br />
than scanning individual wavelengths. FT-NIR is also<br />
capable of much higher resolution than dispersive<br />
instruments, which is important in the pharmaceutical<br />
and biopharmaceutical industry.<br />
43%<br />
FT-NIR is becoming increasingly popular for<br />
process analytical technology (PAT) and other<br />
online applications in the pharmaceutical and<br />
biopharmaceutical industry, such as monitoring<br />
drying and blending processes. The global market<br />
for process FT-NIR in the pharmaceutical and<br />
biopharmaceutical industry in 2010 was more than $21<br />
million, and it is expected to continue to see annual<br />
Bruker<br />
Thermo Scientific<br />
ABB<br />
AIT<br />
Buchi<br />
Yokogawa<br />
Other<br />
Biopharmaceutical and pharmaceutical process FT-NIR<br />
vendor share in 2010.<br />
growth in the mid-teens for the<br />
foreseeable future. At least a half<br />
dozen instrument vendors are<br />
significant competitors in the<br />
market.<br />
The foregoing data were<br />
extracted from SDi’s market<br />
analysis and perspectives<br />
report entitled Biotech &<br />
Pharmaceutical Process Analysis:<br />
PAT Instrumentation and More, March 2011. For more<br />
information, contact Stuart Press, Vice President,<br />
Strategic Directions International, Inc., 6242<br />
Westchester Parkway, Suite 100, Los Angeles, CA<br />
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12 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
three key science agencies in 2012.<br />
The National Science Foundation,<br />
the Department of Energy’s Office of<br />
Science, and the National Institute<br />
of Standards and Technology<br />
Laboratories would benefit from the<br />
proposed additional funding, which<br />
amounts to $13.9 billion in total<br />
funding for the three agencies.<br />
Federal Reserve Chairman Ben<br />
Bernanke, who said that government<br />
spending on research and development<br />
can help boost economic growth,<br />
recently backed Obama.<br />
“The primary economic rationale<br />
for a government role in R&D is that,<br />
absent such intervention, the private<br />
market would not adequately supply<br />
certain types of research,” Bernanke<br />
said at a Georgetown University<br />
conference in May.<br />
For past coverage of this topic,<br />
please see, “Ongoing Battle over 2011<br />
U.S. Budget May Affect President’s<br />
Plan for Additional Science<br />
Investment in 2012” at<br />
www.chromatographyonline.com<br />
Mass Spectrometry<br />
Provides New Insight in<br />
Stroke Research<br />
New research conducted using<br />
mass spectrometers has provided<br />
insight into key areas of stroke<br />
evaluation and treatment. Led by<br />
MingMing Ning, a clinical neurologist<br />
and researcher at the Clinical<br />
Proteomics Research Center at<br />
Massachusetts General Hospital<br />
(Boston, Massachusetts), the research<br />
provides potentially significant new insight<br />
into patent foramen ovale (PFO) and its<br />
connection with strokes. PFO refers to a<br />
congenital heart abnormality, which leaves<br />
open a passage between the left and right<br />
sides of the heart, enabling blood clots to<br />
travel from the leg to the brain.<br />
Strokes are the leading cause of<br />
serious long-term disability in the<br />
United States, and with PFO affecting<br />
25% of the worldwide population,<br />
the potential health impacts are<br />
significant. Identification of potential<br />
biomarkers in mass spectrometry<br />
data derived from the collaborative<br />
research provides scientists with<br />
new insights into how PFO can be<br />
related to strokes. If confirmed,<br />
these insights may be important in<br />
helping doctors to select the most<br />
appropriate treatment for individual<br />
PFO stroke patients.<br />
The research, conducted<br />
by Thermo Fisher Scientific’s<br />
Biomarker Research Initiatives<br />
in Mass Spectrometry Center in<br />
collaboration with Massachusetts<br />
General Hospital, Harvard University,<br />
has also led to potential insights<br />
in the understanding of tissue<br />
plasminogen activator (tPA) in<br />
stroke treatment. tPA is a drug<br />
that can be safely administered<br />
only within a very short window<br />
of time after stroke symptoms<br />
occur. The treatment, which<br />
works by dissolving blood clots,<br />
has proven highly effective, but<br />
involves significant risks. Only 5%<br />
of patients fit the timeframe criteria<br />
within which it is safe to administer<br />
tPA. Through the use of mass<br />
spectrometry–based proteomics<br />
workflows, data from the research<br />
may help scientists identify a wider<br />
scope of patients who might benefit<br />
from tPA.<br />
Raman <strong>Spectroscopy</strong> May<br />
Enable Rapid Diagnosis of<br />
Skin Cancers<br />
A new diagnostic device based on<br />
Raman spectroscopy could assist<br />
physicians with the early detection<br />
of skin cancers. The system is being<br />
studied by Harvey Lui, a professor<br />
of dermatology and chair of the<br />
department of dermatology and<br />
skin science at the University of<br />
British Columbia (Vancouver, British<br />
Colombia). Lui is the coinventor of<br />
the device, which he has licensed to<br />
Verisante (Vancouver).<br />
In preliminary data published in<br />
2008, Lui and colleagues observed<br />
289 skin cancers and benign lesions,<br />
and found that skin cancers could<br />
be distinguished from benign skin<br />
lesions with a sensitivity of 91%<br />
and specificity of 75%. Malignant<br />
melanoma could be distinguished<br />
from benign pigmented lesions with<br />
a sensitivity of 97% and a specificity<br />
of 78%.<br />
Lui says the new device overcomes<br />
one of the key limitations of using<br />
Raman spectroscopy in medicine,<br />
which is the amount of time needed<br />
to acquire data.<br />
“In the past, to collect Raman data<br />
from the skin, the patient would have<br />
to sit still for 20 minutes, and that<br />
is not practical,” Lui said in a May 1<br />
article in Dermatology Times. “But<br />
now it’s possible to acquire this signal<br />
within seconds, and that’s been the<br />
breakthrough.”<br />
Another advantage of the system, Lui<br />
says, is that it is user-friendly and can<br />
be used easily by technicians, and this<br />
does not require the extensive training<br />
that confocal microscopy does.<br />
The device, called the Verisante<br />
Aura, has been approved for use in<br />
Canada and Europe, but US approval<br />
is not expected until next year.<br />
X-ray and AFM Study<br />
of Volcanic Ash<br />
Particles Produces<br />
Risk-Assessment Protocol<br />
A paper published by a joint Icelandic<br />
and Danish team in the journal,<br />
Proceedings of the National Academy<br />
of Sciences (April 25, 2011), provides<br />
evidence that a move to ground<br />
European aircraft was justified<br />
after an April 14, 2010, volcanic<br />
event allowed meltwaters from the<br />
Eyjafjallaökull glacier to mix with<br />
hot magma from the volcanic site,<br />
sending fine ash into the jet stream.<br />
The team used X-ray photoelectron<br />
spectroscopy and atomic force<br />
microscopy to assess toxicity risk and<br />
to determine the composition of the<br />
individual ash particles.<br />
The study involved taking a unique<br />
set of dry ash samples collected<br />
immediately after the explosive event<br />
and comparing the samples with<br />
fresh ash from a later, more typical<br />
eruption. Using nanotechniques<br />
custom-designed for studying natural<br />
materials, the team explored the<br />
physical and chemical nature of the<br />
ash to determine if fears about health<br />
and safety were justified. Additionally,<br />
they developed a protocol that will<br />
serve for assessing risks during a<br />
future event. ◾
14 <strong>Spectroscopy</strong> 26(6) June 2011<br />
www.spectroscopyonline.com<br />
The Baseline<br />
Maxwell’s Equations, Part II<br />
This is the second part of a multipart series on Maxwell’s equations of electromagnetism. The<br />
ultimate goal is a definitive explanation of these four equations; readers will be left to judge<br />
how definitive it is. Please note that figures are being numbered sequentially throughout this<br />
series, which is why the first figure in this column is Figure 7. Another note: This is going to get<br />
a bit mathematical. It can’t be helped: models of the physical universe, like Newton’s second<br />
law F = ma, are based in math. So are Maxwell’s equations.<br />
David W. Ball<br />
James Clerk Maxwell (Figure 7) was born in 1831<br />
in Edinburgh, Scotland. His unusual middle name<br />
derives from his uncle, who was the 6th Baronet<br />
Clerk of Penicuik (pronounced “penny-cook”), a<br />
town not far from Edinburgh. Clerk was, in fact, the<br />
original family name; Maxwell’s father, John Clerk,<br />
adopted the surname Maxwell after receiving a substantial<br />
inheritance from a family named Maxwell.<br />
By most accounts, James Clerk Maxwell (hereafter<br />
referred to as simply “Maxwell”) was an intelligent but<br />
relatively unaccomplished student.<br />
He began blossoming in his early teens, however,<br />
becoming interested in mathematics (especially geometry).<br />
He eventually attended the University of<br />
Edinburgh and, later, Cambridge University, where<br />
he graduated in 1854 with a degree in mathematics.<br />
He stayed on for a few years as a fellow, then moved<br />
to Marischal College in Aberdeen. When Marischal<br />
merged with another college to form the University<br />
of Aberdeen in 1860, Maxwell was laid off (an action<br />
for which the university should still be kicking itself,<br />
but who can foretell the future?) and he found another<br />
position at King’s College London (later the University<br />
of London). He returned to Scotland in 1865, only to<br />
go back to Cambridge in 1871 as the first Cavendish<br />
Professor of Physics. He died of abdominal cancer in<br />
November 1879 at the relatively young age of 48; curiously,<br />
his mother died of the same ailment and at the<br />
same age, in 1839.<br />
Figure 7: James Clerk Maxwell as a young man (holding a color wheel<br />
he invented) and as an older man.<br />
Although he had a relatively short career, Maxwell<br />
was very productive. He made contributions to color<br />
theory and optics (indeed, the first photo in Figure 7<br />
shows Maxwell holding a color wheel of his own invention)<br />
and actually produced the first true color photograph<br />
as a composite of three images. He made major<br />
contributions to the development of the kinetic molecular<br />
theory of gases, for which the “Maxwell-Boltzmann<br />
distribution” is named partially after him. He also<br />
made major contributions to thermodynamics, deriving<br />
the relations that are named after him and devising a<br />
thought experiment about entropy that was eventually
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16 <strong>Spectroscopy</strong> 26(6) June 2011<br />
www.spectroscopyonline.com<br />
ing of electricity and magnetism,<br />
concisely summarizing their behaviors<br />
with four mathematical<br />
expressions known as Maxwell’s<br />
equations of electromagnetism. He<br />
was strongly influenced by Faraday’s<br />
experimental work, believing<br />
that any theoretical description of<br />
a phenomenon must be grounded<br />
in phenomenological observations.<br />
Maxwell’s equations essentially<br />
summarize everything about classical<br />
electrodynamics, magnetism,<br />
and optics, and were only supplanted<br />
when relativity and quantum<br />
mechanics revised our understanding<br />
of the natural universe at<br />
certain limits. Far away from those<br />
limits, in the realm of classical<br />
physics, Maxwell’s equations still<br />
rule just as Newton’s equations of<br />
motion rule under normal conditions.<br />
Figure 8: Maxwell proved mathematically that the rings of Saturn couldn’t be solid objects, but<br />
were likely an agglomeration of smaller bodies. This image of a back-lit Saturn is a composite of<br />
several images taken by the Cassini spacecraft in 2006. Depending on the reproduction, you may<br />
be able to make out a tiny bluish dot in the 10 o’clock position just inside the second outermost<br />
diffuse ring. That’s Earth.<br />
y axis (ordinate)<br />
x axis (abscissa)<br />
Figure 9: A plot of a straight line, which has a constant slope m, given by Δy/Δx.<br />
x<br />
y<br />
called “Maxwell’s demon.” He demonstrated<br />
mathematically that the<br />
rings of Saturn could not be solid,<br />
but must instead be composed of<br />
relatively tiny (relative to Saturn,<br />
of course) particles — a hypothesis<br />
that was supported spectroscopically<br />
in the late 1800s but finally directly<br />
observed the first time when the<br />
Pioneer 11 and Voyager 1 spacecraft<br />
passed through the Saturnian system<br />
in the early 1980s (Figure 8).<br />
Maxwell also made seminal<br />
contributions to the understand-<br />
A Calculus Primer<br />
Maxwell’s laws are written in the<br />
language of calculus. Before we<br />
move forward with an explicit discussion<br />
of the first equation, here<br />
we deviate to a review of calculus<br />
and its symbols.<br />
Calculus is the mathematical<br />
study of change. Its modern form<br />
was developed independently by<br />
Isaac Newton and the German<br />
mathematician Gottfried Leibnitz<br />
in the late 1600s. Although Newton’s<br />
version was used heavily in<br />
his influential Principia Mathematica<br />
(in which Newton used calculus<br />
to express a number of fundamental<br />
laws of nature), it is Leibnitz’s<br />
notations that are commonly used<br />
today. An understanding of calculus<br />
is fundamental to most scientific<br />
and engineering disciplines.<br />
Consider a car moving at constant<br />
velocity. Its distance from<br />
an initial point (arbitrarily set<br />
as a position of 0) can be plotted<br />
as a graph of distance from zero<br />
versus time elapsed. Commonly,<br />
the elapsed time is called the independent<br />
variable and is plotted on<br />
the x axis of a graph (called the abscissa)<br />
while distance traveled from<br />
the initial position is plotted on the<br />
y axis of the graph (called the ordinate).<br />
Such a graph is plotted in<br />
Figure 9. The slope of the line is a<br />
measure of how much the ordinate<br />
changes as the abscissa changes;<br />
that is, slope m is defined as<br />
m = ∆y<br />
∆x<br />
[1]<br />
For the straight line shown in<br />
Figure 9, the slope is constant, so<br />
m has a single value for the entire<br />
plot. This concept gives rise to the<br />
general formula for any straight
©2011 PerkinElmer, Inc. 400217_02. All rights reserved. PerkinElmer ® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.<br />
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18 <strong>Spectroscopy</strong> 26(6) June 2011<br />
www.spectroscopyonline.com<br />
y axis<br />
line in two dimensions, which is<br />
y = mx + b [2]<br />
where y is the value of the ordinate,<br />
x is the value of the abscissa, m is<br />
the slope, and b is the y-intercept,<br />
which is where the plot would<br />
intersect with the y axis. Figure<br />
x axis<br />
Figure 10: A plot of a curve, showing (with the thinner lines) the different slopes at two different<br />
points. Calculus helps us determine the slopes of curved lines.<br />
x<br />
f (x,y)<br />
δf<br />
δx<br />
Figure 11: For a function of several variables, a partial derivative is a derivative in only one<br />
variable. The line represents the slope in the x direction.<br />
9 shows a plot that has a positive<br />
value of m. In a plot with a negative<br />
value of m, it would be going down,<br />
not up, as you go from left to right.<br />
A horizontal line has a value of 0<br />
for m; a vertical line has a slope of<br />
infinity.<br />
Many lines are not straight.<br />
Rather, they are curves. Figure 10<br />
y<br />
gives an example of a plot that is<br />
curved. The slope of a curved line<br />
is more difficult to define than that<br />
of a straight line because the slope<br />
is changing. That is, the value of<br />
the slope depends on the point (x,<br />
y) of the curve you’re at. The slope<br />
of a curve is the same as the slope<br />
of the straight line that is tangent<br />
to the curve at that point (x, y).<br />
Figure 10 shows the slopes at two<br />
different points. Because the slopes<br />
of the straight lines tangent to the<br />
curve at different points are different,<br />
the slopes of the curve itself at<br />
those two points are different.<br />
Calculus provides ways of determining<br />
the slope of a curve, in any<br />
number of dimensions (Figure 10 is<br />
a two-dimensional plot, but we recognize<br />
that functions can be functions<br />
of more than one variable, so<br />
plots can have more dimensions,<br />
or variables, than two). We have<br />
already seen that the slope of a<br />
curve varies with position. That<br />
means that the slope of a curve is<br />
not a constant; rather, it is a function<br />
itself. We are not concerned<br />
about the methods of determining<br />
the functions for the slopes of<br />
curves here; that information can<br />
be found in a calculus text. Instead,<br />
we are concerned with how they<br />
are represented.<br />
The word that calculus uses for<br />
the slope of a function is derivative.<br />
The derivative of a straight line is<br />
simply m, its constant slope. Recall<br />
that we mathematically defined the<br />
slope m above using “Δ” symbols,<br />
where Δ is the Greek capital letter<br />
delta. Δ is used generally to represent<br />
“change”, as in ΔT (change<br />
in temperature) or Δy (change in y<br />
coordinate). For straight lines and<br />
other simple changes, the change<br />
is definite; in other words, it has a<br />
specific value.<br />
In a curve, the change Δy is different<br />
for any given Δx because the slope<br />
of the curve is constantly changing.<br />
Thus, it is not proper to refer to a definite<br />
change because — to overuse a<br />
word — the definite change changes<br />
during the course of the change. What<br />
we have to do is a thought experiment:
www.spectroscopyonline.com June 2011 <strong>Spectroscopy</strong> 26(6) 19<br />
z<br />
F = 3i + 4j + 5k<br />
On-line<br />
NIR<br />
Spectrometers<br />
x<br />
i<br />
k<br />
j<br />
Figure 12: The definition of the unit vectors i, j, and k, and an example of how any vector can be<br />
expressed in terms of how many of each unit vector.<br />
y<br />
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• Faster integration times<br />
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y<br />
x<br />
Figure 13: An example of a vector function F = xi + yj. Each point in two dimensions defines<br />
a vector. Although only 12 individual values are illustrated here, in reality this vector function is a<br />
continuous, smooth function on both dimensions.<br />
We have to imagine that the change<br />
is infinitesimally small over both the<br />
x and y coordinates. This way, the<br />
actual change is confined to an infinitesimally<br />
small portion of the curve:<br />
a point, not a distance. The point<br />
involved is the point at which the<br />
straight line is tangent to the curve<br />
(Figure 10).<br />
Rather than using “Δ” to represent<br />
an infinitesimal change, calculus<br />
starts by using “d”. Rather than using<br />
m to represent the slope, calculus<br />
puts a prime on the dependent variable<br />
as a way to represent a slope<br />
(which, remember, is a function and<br />
not a constant). Thus, for a curve we<br />
have for the slope y′:<br />
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20 <strong>Spectroscopy</strong> 26(6) June 2011<br />
www.spectroscopyonline.com<br />
|a|cosθ<br />
[3]<br />
as our definition for the slope of<br />
that curve.<br />
We hinted earlier that functions<br />
may depend on more than one<br />
a<br />
θ<br />
b<br />
Figure 14: Graphical representation of the dot product of two vectors. The dot product gives<br />
the amount of one vector that contributes to the other vector. Understand that an equivalent<br />
graphical representation would have the b vector projected into the a vector. In both cases, the<br />
overall scalar results are the same.<br />
(a)<br />
(b)<br />
Force<br />
FRAGILE<br />
FRAGILE<br />
Force<br />
Displacement<br />
Displacement<br />
Figure 15: Work is defined as a dot product of a force vector and a displacement vector. (a) If<br />
the two vectors are parallel, they reinforce and work is performed. (b) If the two vectors are<br />
perpendicular, no work is performed.<br />
y = dy<br />
dx<br />
variable. If that is the case, how do<br />
we define the slope? First, we define<br />
a partial derivative as the derivative<br />
of a multivariable function<br />
with respect to only one of its variables.<br />
We assume that the other<br />
variables are held constant. Instead<br />
of using a “d” to indicate a partial<br />
derivative, we use the lowercase<br />
Greek delta “δ”. It is also common<br />
to explicitly list the variables being<br />
held constant as subscripts to the<br />
derivative, although this can be<br />
omitted because it is understood<br />
that a partial derivative is a onedimensional<br />
derivative. Thus we<br />
have<br />
∂f ∂f<br />
= =<br />
∂x ∂x<br />
'<br />
f<br />
x ()<br />
y,z,...<br />
[4]<br />
spoken as “the partial derivative<br />
of the function f(x,y,z,…) with<br />
respect to x.” Graphically, this corresponds<br />
to the slope of the multivariable<br />
function f in the x dimension,<br />
as shown in Figure 11.<br />
The total derivative of a function,<br />
df, is the sum of the partial<br />
derivatives in each dimension; that<br />
is, with respect to each variable individually.<br />
For a function of three<br />
variables, f(x,y,z), the total derivative<br />
is written as<br />
∂f ∂f ∂f<br />
df = dx+ dy+<br />
dz<br />
∂x ∂y ∂z<br />
[5]<br />
where each partial derivative is the<br />
slope with respect to each individual<br />
variable and dx, dy, and dz are the<br />
finite changes in the x, y, and z directions.<br />
The total derivative has as many<br />
terms as the overall function has variables.<br />
If a function is based in threedimensional<br />
space, as is commonly<br />
the case for physical observables, then<br />
there are three variables and so three<br />
terms in the total derivative.<br />
When a function typically generates<br />
a single numerical value<br />
that is dependent on all of its variables,<br />
it is called a scalar function.<br />
An example of a scalar function<br />
might be<br />
F(x,y) = 2x – y 2 [6]<br />
According to this definition, F(4,2)<br />
= 2∙4 – 2 2 = 8 – 4 = 4. The final<br />
value of F(x,y), 4, is a scalar: it has<br />
magnitude but no direction.<br />
A vector function is a function<br />
that determines a vector, which is
www.spectroscopyonline.com June 2011 <strong>Spectroscopy</strong> 26(6) 21<br />
a quantity that has magnitude and<br />
direction. Vector functions can be<br />
easily expressed using unit vectors,<br />
which are vectors of length 1<br />
along each dimension of the space<br />
involved. It is customary to use<br />
the representations i, j, and k to<br />
represent the unit vectors in the x,<br />
y, and z dimensions, respectively<br />
(Figure 12). Vectors are typically<br />
represented in print as boldfaced<br />
letters. Any random vector can be<br />
expressed as, or decomposed into,<br />
a certain number of i vectors, j<br />
vectors, and k vectors as is demonstrated<br />
in Figure 12. A vector<br />
function might be as simple as<br />
F = xi + yj [7]<br />
in two dimensions, which is illustrated<br />
in Figure 13 for a few<br />
discrete points. Although only a<br />
few discrete points are shown in<br />
Figure 13, understand that the vector<br />
function is continuous. That is,<br />
it has a value at every point in the<br />
graph.<br />
One of the functions of a vector<br />
that we will have to evaluate is<br />
called a dot product. The dot product<br />
between two vectors a and b is<br />
represented and defined as<br />
a∙b = |a||b|cosϴ [8]<br />
Thus, if the two vectors are<br />
parallel (ϴ = 0° so cosϴ = 1) the<br />
work is maximized, but if the two<br />
vectors are perpendicular to each<br />
other (ϴ = 90° so cosϴ = 0), the<br />
object does not move and no work<br />
is done (Figure 15).<br />
. . . But We’ll Have to Wait<br />
I hope you’ve followed so far —<br />
but so far, it’s been easy. To truly<br />
understand Maxwell’s first equation,<br />
we need to do a bit more advanced<br />
stuff. Don’t worry — our<br />
job in “The Baseline” is to talk<br />
you through it. Unfortunately,<br />
we’re going to have to wait<br />
until the next installment to<br />
pursue the more advanced stuff<br />
and get to the heart of Maxwell’s<br />
first equation.<br />
For more information on this topic, please visit:<br />
www.spectroscopyonline.com/ball<br />
UV/Vis and NIR Fiber Optic<br />
Probes for Process and<br />
Laboratory applications<br />
David W. Ball is<br />
normally a professor of<br />
chemistry at Cleveland<br />
State University in Ohio.<br />
For a while, though, things<br />
will not be normal: starting<br />
in July 2011 and for the<br />
commencing academic<br />
year, David will be serving as Distinguished<br />
Visiting Professor at the United States Air<br />
Force Academy in Colorado Springs, Colorado,<br />
where he will be teaching chemistry to<br />
Air Force cadets. He still, however, has two<br />
books on spectroscopy available through<br />
SPIE Press, and just recently published two<br />
new textbooks with Flat World Knowledge.<br />
Despite his relocation, he still can be contacted<br />
at d.ball@csuohio.edu. And finally,<br />
while at USAFA he will still be working on<br />
this series, destined to become another<br />
book at an SPIE Press web page near you.<br />
where |a| represents the magnitude<br />
(that is, length) of a, |b| is the magnitude<br />
of b, and cosϴ is the cosine<br />
of the angle between the two vectors.<br />
The dot product is sometimes<br />
called the scalar product because<br />
the value is a scalar, not a vector.<br />
The dot product can be thought of<br />
physically as how much one vector<br />
contributes to the direction of the<br />
other vector, as shown in Figure<br />
14. A fundamental definition that<br />
uses the dot product is that for<br />
work, w, which is defined in terms<br />
of the force vector F and the displacement<br />
vector of a moving object,<br />
s, and the angle between these<br />
two vectors:<br />
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coupling via SMA<br />
or Hellma Interface<br />
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process control: Hellma Fiber Optic<br />
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w = F∙s = |F||s|cosϴ [9]<br />
Transmission Reflection ATR Fluorescence Transflection
22 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
Chemometrics in <strong>Spectroscopy</strong><br />
Classical Least Squares, Part VI:<br />
Spectral Results<br />
We continue to examine in detail the spectral behavior of three-component mixtures.<br />
Howard Mark and Jerome Workman, Jr.<br />
This column is the continuation of our discussion of<br />
the classical least squares approach to calibration<br />
(1–5). In this installment, as in the previous one (5),<br />
we will be dealing largely with figures, and the spectra<br />
therein. So far, we have looked at the spectra of the pure<br />
components comprising the ternary mixtures we are<br />
working with. We also have looked at the spectra of all<br />
the mixtures overlaid on each other.<br />
One important reason to perform this extensive exercise<br />
of examining spectra is to address, and hopefully<br />
clear up, a misconception some people have about nearinfrared<br />
(NIR) spectra. Because of its history, NIR spectroscopy<br />
sometimes is believed to rely on, and require,<br />
the “magic” of chemometric analysis to obtain meaningful<br />
scientific results. But that’s not always true. That perception<br />
has arisen because NIR measurements most often<br />
are made on samples that are powdered solids, part of a<br />
dynamic mechanism, or involve other difficult conditions<br />
that often make other types of spectral measurements<br />
impossible.<br />
This has created an impression that NIR exists in a<br />
Celebrating 25 Years<br />
The editors congratulate Howard Mark and<br />
Jerry Workman for 25 years of statistics and<br />
chemometrics columns in <strong>Spectroscopy</strong>.<br />
universe of its own, disconnected from the rest of science.<br />
Therefore, we take this opportunity to emphasize<br />
(and maybe overemphasize) the fact that NIR is not some<br />
“magical” technique that is different from the rest of the<br />
universe, but in fact is the same spectroscopy we are all<br />
used to seeing in other spectral regions. When samples<br />
are presented to a spectrometer, they behave the same<br />
way in the NIR as they do in the UV, visible, mid-IR, or<br />
any other region.<br />
In the current experiment, we have a situation where<br />
clear liquid samples are used, and measured in a cuvette<br />
having plane parallel windows — the near-ideal conditions<br />
that are normally used for any spectral region. In<br />
this way, we can demonstrate that NIR spectra, under<br />
those conditions, do indeed behave the same way as spectra<br />
in other spectral regions do.<br />
Let us look at the three sets of two-component mixtures<br />
that the experimental design includes. These are<br />
presented in Figures 1–3. In these figures, we first present<br />
the full spectrum, and then for each mixture we present<br />
the spectra of the mixtures in the several subranges that<br />
contain the useful absorbance bands.<br />
Examining these spectra, we see some features that<br />
were partially obscured when the spectra from all the<br />
mixtures were plotted together. One effect that was<br />
hidden by the overlapping spectra was the presence of<br />
isosbestic points. Although Figure 5e from part V of this<br />
column series (5) shows a ternary isosbestic point, that<br />
is rare; for the most part isosbestic points are not seen
www.spectroscopyonline.com<br />
June 2011 <strong>Spectroscopy</strong> 26(6) 23<br />
(b)<br />
(a) 1<br />
0.9<br />
-0.2 -0.1<br />
4000 5000 6000 7000 8000 9000 10,000 4000 4100 4200 4300 4400 4500 4600 4700 4800 4900 5000<br />
0.8<br />
0.8<br />
0.7<br />
0.6<br />
0.6<br />
0.5<br />
0.4<br />
0.4<br />
0.3<br />
0.2<br />
0.2<br />
0.1<br />
0<br />
0<br />
Wavelength<br />
Transmittance<br />
(c) 1<br />
(d)<br />
1<br />
Transmittance<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
0<br />
5000 5500 6000 6500<br />
Wavelength<br />
Transmittance<br />
0.95<br />
0.9<br />
0.85<br />
0.8<br />
0.75<br />
0.7<br />
0.65<br />
6500 6600 6700 6800 6900 7000 7100 7200 7300 7400 7500<br />
Wavelength<br />
(e)<br />
1<br />
0.95<br />
0.9<br />
Transmittance<br />
0.85<br />
0.8<br />
0.75<br />
0.7<br />
0.65<br />
7500 8000 8500 9000<br />
Wavelength<br />
Figure 1: Transmission spectra of mixtures of toluene and dichloromethane: (a) full spectrum from 4000 to 10,000 cm -1 ; (b) 4000–5000 cm -1 ; (c)<br />
5000–6500 cm -1 ; (d) 6500–7500 cm -1 ; (e) 7500–9000 cm -1 .
24 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
(a)<br />
1<br />
0.8<br />
0.6<br />
(b) 0.8<br />
0.7<br />
0.6<br />
0.5<br />
Transmittance<br />
0.4<br />
0.2<br />
Transmittance<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
0<br />
0<br />
-0.2<br />
4000 5000 6000 7000 8000 9000 10,000<br />
Wavelength<br />
-0.1<br />
4000 4100 4200 4300 4400 4500 4600 4700 4800 4900 5000<br />
Wavelength<br />
(c)<br />
1<br />
(d)<br />
1<br />
0.9<br />
0.8<br />
0.95<br />
0.7<br />
0.9<br />
Transmittance<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
0<br />
5000 5500 6000 6500<br />
Wavelength<br />
Transmittance<br />
0.85<br />
0.8<br />
0.75<br />
0.7<br />
0.65<br />
6500 6600 6700 6800 6900 7000 7100 7200 7300 7400 7500<br />
Wavelength<br />
(e)<br />
1<br />
0.95<br />
0.9<br />
Transmittance<br />
0.85<br />
0.8<br />
0.75<br />
0.7<br />
0.65<br />
7500 8000 8500 9000<br />
Wavelength<br />
Figure 2: Transmission spectra of mixtures of toluene and n-heptane: (a) 4500–10,000 cm -1 ; (b) 4000–5000 cm -1 ; (c) 5000–6500 cm -1 ; (d) 6500–<br />
7500 cm -1 ; (e) 7700–9000 cm -1 .
www.spectroscopyonline.com<br />
June 2011 <strong>Spectroscopy</strong> 26(6) 25<br />
(a)<br />
Transmittance<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
(b) 0.9<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
Transmittance<br />
0<br />
-0.2<br />
4000 5000 6000 7000 8000 9000 10,000<br />
Wavelength<br />
0.1<br />
0<br />
-0.1<br />
4000 4100 4200 4300 4400 4500 4600 4700 4800 4900 5000<br />
Wavelength<br />
(c) 0.1<br />
0.9<br />
(d)<br />
1<br />
0.95<br />
Transmittance<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
Transmittance<br />
0.9<br />
0.85<br />
0.8<br />
0.75<br />
0.7<br />
0.65<br />
5000 5500 6000 6500<br />
Wavelength<br />
(e) 1<br />
6500 6600 6700 6800 6900 7000 7100 7200 7300 7400 7500<br />
Wavelength<br />
0.95<br />
0.9<br />
Transmittance<br />
0.85<br />
0.8<br />
0.75<br />
0.7<br />
0.65<br />
7500 8000 8500 9000<br />
Wavelength<br />
Figure 3: Transmission spectra of mixtures of dichloromethane and n-heptane: (a) 4000 to 10,000 cm -1 ; (b) 4000–5000 cm -1 ; (c) 5000–6500 cm -1 ;<br />
(d) 6500–7500 cm -1 ; (e) 7600–9000 cm -1 .<br />
in the previous presentations of the<br />
spectra because the other spectra in<br />
the set obscure the isosbestic points.<br />
Examining the spectra of the<br />
two-component mixtures, however,<br />
reveals a plethora of isosbestic points.<br />
In fact, when we look at the expansions<br />
of the wavelength ranges, we<br />
find that all three sets of two-component<br />
mixtures contain multiple<br />
isosbestic points.<br />
Another phenomenon more easily<br />
seen in the spectra of the twocomponent<br />
mixtures is the presence<br />
of the expected nonlinearity of the<br />
transmission spectra with respect<br />
to composition, especially for the<br />
stronger absorbance bands. Because<br />
the strongest absorbance bands in<br />
the spectra generally fall in the range<br />
of 5000–6500 cm -1 , this nonlinearity<br />
is very visible in the bands of the<br />
two-component mixtures falling in<br />
this range. Examples where this ef-
26 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
(a)<br />
2<br />
(b)<br />
1.6<br />
Wavelength<br />
1.8<br />
1.6<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
Wavelength<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
4000 5000 6000 7000 8000 9000 10,000<br />
Absorbance<br />
0<br />
4500 4550 4600 4650 4700 4750 4800 4850 4900 4950 5000<br />
Absorbance<br />
(c)<br />
2<br />
(d)<br />
0.2<br />
1.8<br />
0.18<br />
Wavelength<br />
1.6<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
Wavelength<br />
0.16<br />
0.14<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.2<br />
0<br />
5000 5500 6000 6500<br />
Absorbance<br />
0.04<br />
0.02<br />
6500 6600 6700 6800 6900 7000 7100 7200 7300 7400 7500<br />
Absorbance<br />
(e) 0.18<br />
0.16<br />
0.14<br />
Wavelength<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
7500 8500 9000<br />
8000<br />
Absorbance<br />
Figure 4: Absorption spectra of mixtures of toluene and dichloromethane: (a) from 4500 to 10,000 cm -1 ; (b) 4500–5000 cm -1 ; (c) 4800–6300 cm -1 ;<br />
(d) 6500–7500 cm -1 ; (e) 8000–9000 cm -1 .<br />
fect is prominent include the band<br />
at 5700 cm -1 in Figure 1c, the band<br />
at 8400 cm -1 in Figure 1e, and the<br />
band at 5700 cm -1 in Figure 3c. In<br />
fact, the “clipping” that we previously<br />
observed in the 4000–5000 cm -1 region<br />
now can be seen as simply an<br />
exaggerated version of this effect; the<br />
absorbance bands in that region are<br />
so strong that effectively no energy is<br />
left to come through the sample.<br />
The nonlinearity is not necessarily<br />
visible in all spectra, of course.<br />
For the compression of the spectra<br />
to become easily visible, simply having<br />
a part of the spectrum with high<br />
absorbance does not suffice. It is also<br />
necessary for the transmittance at<br />
the given wavelength to vary over<br />
an appreciable range in the different<br />
samples. If the transmittance is<br />
uniformly high, as is the case for the<br />
band around 7270 cm -1 in Figure 1d,<br />
then the nonlinearity does not com-
www.spectroscopyonline.com<br />
June 2011 <strong>Spectroscopy</strong> 26(6) 27<br />
(a)<br />
1.6<br />
1.4<br />
1.2<br />
(a) 2<br />
1.8<br />
1.6<br />
1.4<br />
wavelength<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
Wavelength<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
(b)<br />
0.2<br />
0<br />
4000 5000 6000 7000<br />
Absorbance<br />
1.6<br />
1.4<br />
1.2<br />
8000 9000 10,000<br />
0.2<br />
(b) 0.7<br />
0<br />
4000 5000 6000 7000 8000 9000 10,000<br />
Absorbance<br />
0.6<br />
0.5<br />
wavelength<br />
1<br />
0.8<br />
0.6<br />
Wavelength<br />
0.4<br />
0.3<br />
0.4<br />
0.2<br />
0.2<br />
0.1<br />
0<br />
4500<br />
(c) 1.4<br />
4550<br />
4600 4650 4700 4750 4800 4850 4900 4950 5000<br />
Absorbance<br />
(c) 2<br />
0<br />
4500 4550 4600 4650 4700 4750 4800 4850<br />
Absorbance<br />
4900 4950 5000<br />
1.2<br />
1.8<br />
1.6<br />
1<br />
1.4<br />
wavelength<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
Wavelength<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
(d) 0.18<br />
0<br />
5000 5500 6000 6500<br />
Absorbance<br />
0.16<br />
0.14<br />
(d) 0.2<br />
0<br />
5000 5500 6000 6500<br />
Absorbance<br />
0.18<br />
0.16<br />
wavelength<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
Wavelength<br />
0.14<br />
0.12<br />
0.1<br />
0.08<br />
0.06<br />
0.04<br />
(e)<br />
0.04<br />
6000 6600 6700 6800 6900 7000 7100 7200 7300 7400 7500<br />
Absorbance<br />
0.2<br />
0.18<br />
0.16<br />
0.14<br />
(e) 0.2<br />
0.02 6500 6600 6700 6800 6900 7000 7100 7200 7300 7400 7500<br />
Absorbance<br />
0.18<br />
0.16<br />
0.14<br />
wavelength<br />
0.12<br />
0.1<br />
Wavelenght<br />
0.12<br />
0.1<br />
0.08<br />
0.08<br />
0.06<br />
0.06<br />
0.04<br />
0.04<br />
0.02<br />
7500 8000 8500 9000<br />
Absorbance<br />
0.02<br />
7500 8000 8500 9000<br />
Absorbance<br />
Figure 5: Absorption spectra of mixtures of toluene and n-heptane: (a)<br />
from 4500 to 10,000 cm -1 ; (b) 4500–5000 cm -1 ; (c) 5000–6500 cm -1 ; (d)<br />
6500–7500 cm -1 ; (e) 7700–9000 cm -1 .<br />
Figure 6: Absorption spectra of mixtures of dichloromethane and<br />
n-heptane: (a) from 4500 to 10,000 cm -1 ; (b) 4500–5000 cm -1 ; (c) 5000–<br />
6500 cm -1 ; (d) 6500–7500 cm -1 ; (e) 7600–9000 cm -1 .
28 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
press the spectra to the point where it<br />
is readily visible to the eye. Similarly,<br />
if the transmittance is low, but is uniformly<br />
low for all the samples of the<br />
set, we do not observe the nonlinearity<br />
because it would not be sufficient<br />
over a small range of transmission<br />
to be observed. An example of this<br />
is the band at 5700 cm -1 in Figure<br />
3c. This behavior of the absorbance<br />
bands, to not show the nonlinearity,<br />
is often associated with an isosbestic<br />
point, as in the case of the band in<br />
Figure 3c.<br />
It is well known this nonlinearity<br />
of transmittance versus composition<br />
in the 5000–6500 cm -1 range, however,<br />
occurs because the transmission<br />
of energy through a clear but<br />
absorbing liquid decreases asymptotically,<br />
but exponentially, to zero.<br />
Therefore we see that although the<br />
composition varies in equal increments<br />
(of 25%, as described in the<br />
experimental section in part V of<br />
this column series [5]), the spectral<br />
differences do not show the same<br />
equal spacing, but are visibly compressed<br />
at the higher absorbance<br />
levels.<br />
To achieve equal spacing of the<br />
spectra for equal changes in composition,<br />
the transmission spectra must<br />
be converted to absorbance spectra.<br />
A set of absorbance spectra paralleling<br />
the transmission spectra seen<br />
in Figures 1–3 is shown in Figures<br />
4–6. As we did with the transmission<br />
spectra, we plotted these absorption<br />
spectra both at the full wavelength<br />
range and in each of the wavelength<br />
ranges of interest. We also have limited<br />
the lower end of the wavelength<br />
range to 4500 cm -1 to prevent the<br />
“zero” transmission values from<br />
being converted to extremely high<br />
absorption values that would compress<br />
the bands at other wavelengths<br />
to the point of invisibility.<br />
We can compare the spacings between<br />
spectra in the various parts of<br />
Figures 4–6 with the spacings in the<br />
corresponding parts of Figures 1–3.<br />
Mostly we see that the spacings have<br />
tended to even out; this can be seen,<br />
for example, by comparing the band<br />
at 5700 cm -1 in Figure 1c with the<br />
corresponding absorbance band in<br />
Figure 4c. Nevertheless, although the<br />
bands in Figure 4c show less compression<br />
in the higher absorbance<br />
spectra than the bands in Figure 1c,<br />
there is still a noticeable amount.<br />
Surprisingly, an opposite effect<br />
sometimes occurs. For example, the<br />
band at roughly 5900 cm -1 in those<br />
same two figures is nearly evenly<br />
spaced in the transmission display,<br />
but shows increasing spacing for the<br />
higher-absorbance spectra.<br />
We will discuss this further in a<br />
future column.<br />
References<br />
(1) H. Mark and J. Workman, <strong>Spectroscopy</strong><br />
25(5), 16–21 (2010).<br />
(2) H. Mark and J. Workman, <strong>Spectroscopy</strong><br />
25(6), 20–25 (2010).<br />
(3) H. Mark and J. Workman, <strong>Spectroscopy</strong><br />
25(10), 22–31 (2010).<br />
(4) H. Mark and J. Workman, <strong>Spectroscopy</strong><br />
26(2), 26–33 (2011).<br />
(5) H. Mark and J. Workman, <strong>Spectroscopy</strong><br />
26(5), 12–22 (2011).<br />
Howard Mark<br />
serves on the Editorial<br />
Advisory Board of<br />
<strong>Spectroscopy</strong> and runs<br />
a consulting service,<br />
Mark Electronics (Suffern,<br />
NY). He can be<br />
reached via e-mail:<br />
hlmark@prodigy.net<br />
Jerome Workman,<br />
Jr. serves on the Editorial<br />
Advisory Board of<br />
<strong>Spectroscopy</strong> and is the<br />
executive vice president<br />
of Engineering at<br />
Unity Scientific, LLC,<br />
(Brookfield, Connecticut).<br />
He is also an adjunct professor at<br />
U.S. National University (La Jolla, California),<br />
and Liberty University (Lynchburg,<br />
Virginia). His email address is<br />
JWorkman04@gsb.columbia.edu<br />
For more information on this topic,<br />
please visit our homepage at:<br />
www.spectroscopyonline.com
Differential ion<br />
Mobility SpectroMetry,<br />
a new Dimension in Selectivity for lc/MS/MS<br />
liVe WebcaSt: Thursday, June 3, 011 at 11:00AM EST<br />
REgiSTER FREE at http://chromatographyonline.com/differential<br />
EvEnT OvERviEw:<br />
This webcast will provide an overview of the recent advances<br />
in differential ion mobility spectrometry and describe its applications<br />
to significantly increase the analytical selectivity of<br />
your LC-MS/MS analyses for challenging samples requiring<br />
advanced separation power. The fundamental principals of<br />
operation and an in depth description of the various applications<br />
possible with this innovation in ion mobility technology<br />
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Discover how this new dimension of selectivity can enhance<br />
performance for any application requiring the separation of<br />
isobaric species, isolation of challenging co-eluting contaminants<br />
and reduction of high background noise finally making<br />
ion mobility spectrometry an effective tool for improving data<br />
quality in the quantitation & characterization of samples requiring<br />
advanced separation power.<br />
WHO SHOULD ATTEND:<br />
Current LC/MS/MS users who are challenged by assays with<br />
isobaric interferences and difficult to separate co-eluting contaminants<br />
and who require a fast, reproducible and easy to use<br />
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without compromising sensitivity<br />
KEY LEARNING OBJECTIVES<br />
• To provide an overview of<br />
the advances in ion mobility<br />
separation<br />
• Demonstrate how innovative<br />
ion mobility separation<br />
advances contribute to<br />
increased selectivity and<br />
improved data quality<br />
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across diverse application<br />
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PRESENTERS:<br />
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Presented by<br />
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Technical Editor<br />
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For questions, contact Jamie Carpenter at jcarpenter@advanstar.com
30 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
Optimizing FT-IR Sampling<br />
for a Method to Determine<br />
the Chemical Composition of<br />
Microbial Materials<br />
The need for new energy sources has been a major concern for many years. The fear<br />
over global warming and CO 2<br />
emissions has drastically increased the worldwide awareness<br />
of this critical problem. The conversion of biomass into fuel is one of the most<br />
promising technologies to replace fossil fuels as a main energy source, particularly for<br />
transportation. Although food crops such as corn and soybeans have been successfully<br />
used to create bioethanol and biodiesel, the use of food crops and viable farmland is not<br />
really a sustainable long-term solution. A great deal of research is being funded to investigate<br />
alternative sources of biomass that can be economically converted into fuel. Algae<br />
and other aquatic species appear to be one of the most promising sources for the large<br />
quantities of biomass required for a successful biofuels program. The concept of producing<br />
biofuels from algae is not a recent idea and government funding for this research<br />
has been significant. A report from the National Renewable Energy Laboratory (Golden,<br />
Colorado) provides an excellent background in this area, describing research that started<br />
in 1978 and extended over 20 years (1). One reason for the interest in algae as a source<br />
of biodiesel is that CO 2<br />
and a source of nutrients are required for biomass production.<br />
In one scenario, large algae “farms” are positioned near power plants or incinerators to<br />
convert their waste CO 2<br />
into biomass. Waste-treatment facilities also could provide most<br />
of the required nutrients.<br />
Steve Lowry<br />
The rapid growth of many microalgae species is not<br />
only valuable for production, but greatly reduces the<br />
time required to optimize the strains for biofuels. A<br />
number of research groups are attempting to increase the<br />
amount of lipid produced by the algae under normal conditions<br />
through genetic improvements. Fourier-transform<br />
infrared (FT-IR) spectroscopy has been used extensively<br />
to characterize the chemical composition of biological<br />
systems including bacteria, single cells, and tissues (2–6).<br />
The infrared spectrum contains peaks that correspond to<br />
the presence of protein, carbohydrates, and lipids, as well<br />
as DNA and other biomolecules commonly found in cells.<br />
In a recent paper, Pistorius and colleagues (7) describe a<br />
method to determine the protein, carbohydrate, and lipid<br />
content in biomass from algae and other microbiological<br />
sources. Their analysis is based on obtaining a high quality<br />
FT-IR spectrum from a sample of microalgae and determining<br />
the amount of specific components in the sample
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32 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
Figure 1: Selecting the protein spectral region in OMNIC TQ Analyst software.<br />
Absorbance<br />
Absorbance<br />
0.12<br />
0.10<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
0.12<br />
0.10<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
*Algae powder by ATR<br />
*Algae deposited on foil ATR<br />
3500 3000<br />
based on specific features in the spectra.<br />
The authors emphasized that the<br />
sample preparation is a key step to<br />
2500 2000 1500 1000<br />
Wavenumbers ( cm-1 )<br />
Figure 2: ATR spectra from powdered algae (top) and algae deposited on an aluminum foil<br />
surface (bottom).<br />
obtaining reproducible results. In this<br />
paper, several different infrared sampling<br />
techniques will be described that<br />
can be used to analyze microbiological<br />
samples. The goal of this work was to<br />
identify a cost-effective technique that<br />
might greatly increase the number of<br />
samples that can be analyzed with automated<br />
spectroscopy.<br />
<strong>Experimental</strong><br />
Portions of dried samples of different<br />
algae specimens were directly<br />
analyzed by attenuated total reflectance<br />
(ATR) spectroscopy. Aqueous<br />
suspensions of the material were<br />
deposited on various substrates for<br />
both transmittance and reflectance<br />
studies. The actual chemical compositions<br />
of the algae samples available<br />
for this study were unknown.<br />
An analytical method modeled after<br />
the work of Pistorius and colleagues<br />
was created using Thermo Scientific<br />
OMNIC TQ Analyst software<br />
(Thermo Fisher Scientific, Waltham,<br />
Massachusetts).<br />
The key parameters from their<br />
work that were used in this analysis<br />
method are shown in Table I.
www.spectroscopyonline.com<br />
June 2011 <strong>Spectroscopy</strong> 26(6) 33<br />
Absorbance<br />
Absorbance<br />
2.0<br />
*Blank PTFE<br />
1.5<br />
1.0<br />
0.5<br />
0.8 Algae on PTFE membrane<br />
0.6<br />
0.4<br />
No Sample<br />
too Tough...<br />
Absorbance<br />
PE card blank<br />
1.5<br />
1.0<br />
0.5<br />
0.7<br />
*Algae on polythylene membrane<br />
Absorbance<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
3500 3000 2500 2000 1500 1000<br />
Wavenumbers (cm -1 )<br />
Figure 3: Transmittance spectra from algae samples deposited on<br />
polyethylene and PTFE microporous films.<br />
0.7 Algae on BaF 2 window<br />
0.6<br />
Absorbance<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
Absorbance<br />
0.1<br />
0.10 Bacteria on silicon substrate<br />
0.08<br />
0.06<br />
0.04<br />
0.02<br />
0.00<br />
0.02<br />
0.04<br />
3500 3000 2500 2000<br />
Wavenumbers ( cm-1 )<br />
1500 1000<br />
Analyze hard materials with<br />
no sample preparation<br />
Monitor structural changes<br />
at high temperatures<br />
Figure 4: An algae sample deposited on barium fluoride and a bacteria<br />
sample deposited on silicon.<br />
When the method was applied to ATR spectra, the<br />
actual scale factors reported in the Pistorius method<br />
were adjusted to account for the different relative intensities<br />
observed with the ATR spectra. Figure 1 shows<br />
the screen in TQ Analyst that sets up the spectral region<br />
used to determine the protein concentration.<br />
FT-IR spectra were obtained from several samples of<br />
algae using ATR spectroscopy, transmission spectroscopy,<br />
reflectance spectroscopy, and infrared microscopy. A<br />
Thermo Scientific Nicolet iS 10 FT-IR spectrometer configured<br />
with a Smart iTR diamond accessory (Thermo Fisher<br />
Scientific) was used to obtain spectra from dried algae. All<br />
spectra were acquired at 4-cm -1 resolution with a room<br />
temperature DTGS (deuterated triglycine sulfate) detector<br />
in less than 1 min. The pressure tower on the accessory<br />
applies a constant pressure on the sample, producing consistent<br />
spectra from the different samples. The transmission<br />
spectra were acquired using the same FT-IR spectrometer<br />
and the Smart OMNI-transmission accessory. The samples<br />
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34 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
with an automated well-plate reader<br />
was used with the OMNIC Array<br />
Automation software to analyze the<br />
samples deposited on the aluminum<br />
foil surface. The infrared microscope<br />
transmission data were obtained with<br />
a Nicolet 6700 FT-IR system and a<br />
Continuum infrared microscope configured<br />
with an automated X,Y stage.<br />
Figure 5: Diagram of the reflectance optics module used in the array autosampler.<br />
Figure 6: Screen showing the Array Automation results using the amount of lipid as the metric<br />
to color the wells.<br />
were deposited from aqueous solution<br />
onto barium fluoride or silicon windows,<br />
a polyethylene microporous<br />
membrane, or polytetrafluoroethylene<br />
(PTFE) membrane. For the reflectance<br />
study, the samples were deposited onto<br />
an aluminum foil surface marked with<br />
96 positions consistent with a standard<br />
well-plate format. A Nicolet 6700 spectrometer<br />
(Thermo Fisher Scientific)<br />
Results and Discussion<br />
ATR spectroscopy is an excellent technique<br />
to rapidly characterize discrete<br />
samples. The dried material is pressed<br />
against the 2-mm diameter ATR crystal<br />
and a spectrum is acquired. The<br />
depth of penetration into the sample<br />
in the ATR experiment is wavelength<br />
dependent and results in relatively<br />
lower intensity of the peaks in the<br />
higher wavenumber region. The peak<br />
intensity is also related to the total<br />
amount of sample in contact with the<br />
crystal. Thus, sample hardness and<br />
particle size can change the intensities<br />
of the peaks slightly, and spectra<br />
should be corrected before calculating<br />
the amount of each component.<br />
Although the samples were prepared<br />
for automated reflectance analysis,<br />
ATR spectra were also acquired from<br />
the algae deposited on the aluminum<br />
foil surface. These spectra were similar<br />
to the ones obtained by placing the<br />
dried algae directly on the ATR crystal.<br />
Figure 2 shows the ATR spectra<br />
from different algae samples that were<br />
acquired.<br />
One of the objectives of this research<br />
was to develop a better understanding<br />
of ways that the automated<br />
sampling techniques created<br />
for pharmaceutical high-throughput<br />
screening systems might be applied<br />
to the analysis of algae. In particular,<br />
can the automated weighing,<br />
dilution, and deposition systems designed<br />
around the 96-well SBS format<br />
improve productivity in FT-IR<br />
analysis of biological materials? A<br />
number of years ago, 3M (St. Paul,<br />
Minnesota) introduced a disposable<br />
IR sampling card based on a polymer<br />
microporous membrane. A publication<br />
by Mosoba and colleagues (8) reports<br />
using a polyethylene microporous<br />
film with this sampling concept
www.spectroscopyonline.com<br />
June 2011 <strong>Spectroscopy</strong> 26(6) 35<br />
to obtain FT-IR spectra from bacteria samples. They created<br />
a multiple-sampling method by stretching the film<br />
across the holes in an autosampler wheel. A plate with 96<br />
holes in a well-plate format or a microscope slide with 16<br />
holes also could be developed for automated sampling.<br />
A major point of these analyses is to measure the<br />
amount of lipid in the algae samples using infrared spectroscopy.<br />
The analytical method described in the Pistorius<br />
publication uses the spectral features in the C-H<br />
stretching region to determine the lipid content. However,<br />
the spectral features from the polyethylene film are<br />
very similar to those from lipids, creating a large cross<br />
interference problem. The PTFE polymer shows no interference<br />
in the C-H stretch region and has no features<br />
in the amide or carbonyl regions, although the strong<br />
infrared peak for PTFE near 1200 cm -1 results in some<br />
spectral distortion near the region employed for the carbohydrate<br />
analysis. Figure 3 shows spectra from the two<br />
polymer films and from algae samples after subtraction<br />
of the spectra from the reference films. Although some<br />
spectral artifacts are observed from the polymer, the use<br />
of microporous polymer film as a sample substrate would<br />
result in a very low cost disposable sampling system.<br />
In a previous project, biological samples were deposited<br />
from a saline solution onto small 5-mm squares of<br />
barium fluoride (BaF 2<br />
) and dried before the acquisition<br />
of spectra in transmittance (2). Barium fluoride is an<br />
excellent IR window and is not soluble in water. However,<br />
it is quite expensive and probably would not be considered<br />
a disposable sample holder by most laboratories.<br />
An alternative approach that looks very promising is to<br />
deposit the samples on small squares of polished silicon<br />
that have been cut from a semiconductor wafer. A number<br />
of surplus double side polished 8-in. silicon wafers<br />
were purchased and were diced into 0.25-in. squares.<br />
Figure 4 shows the spectrum obtained by depositing an<br />
aqueous suspension onto a barium fluoride window and the<br />
spectrum from a bacteria sample deposited onto a silicon<br />
square after subtraction of a silicon reference spectrum.<br />
This figure shows the similarities and differences between<br />
the algae and bacteria samples. A plastic holder was designed<br />
to hold the silicon and BaF 2<br />
squares. For compatibility<br />
with microscope slide handling stages, a 1 × 3 in.<br />
silicon sample holder was also designed, allowing use in a<br />
high throughput sampling system that matches two columns<br />
in the standard 96-well format. Another alternative<br />
sampling technique is to use a single piece of silicon with<br />
96 shallow wells created by a gasket. The silicon piece is<br />
mounted in a frame consistent with the SBS 96-well form<br />
factor. In a related study, samples of bacteria were deposited<br />
and dried on a silicon 96-spot plate (Pike Technologies,<br />
Madison, Wisconsin). Spectra were acquired from<br />
the samples deposited on the plate using a Nicolet 6700<br />
FT-IR spectrometer and a Continuum infrared microscope<br />
configured with a high-precision X,Y stage and a modified<br />
version of the OMNIC Array Automation software. Infrared<br />
microscopy is very valuable for obtaining high quality<br />
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36 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
Table I: Key parameters of the Pistorius method (7) used in this study<br />
Sample X Start X End Slope Intercept<br />
Protein 1477 1590 12.72 -0.27<br />
Lipid 2780 2984 78.96 -2.3<br />
Carbo 1133 1180 2.05 0.07<br />
spectra when the amount of sample is<br />
limited to less than a milligram. The<br />
sampling area in the ATR experiment<br />
and transmission is 2–5 mm, while the<br />
sampling area with an infrared microscope<br />
is routinely 100 µm and can be<br />
less than 10 µm. The Array Automation<br />
software would permit the analysis<br />
of micro-arrays including the SBS<br />
standard 1536-well plate format.<br />
A final, very promising, sampling<br />
technique is automated reflectance<br />
analysis. This involves depositing the<br />
algae samples onto a highly reflecting<br />
surface, such as aluminum foil, in<br />
an array format. In this example, the<br />
samples were deposited in a 96-well<br />
format and analyzed using the reflectance<br />
option with the well plate reader.<br />
The optical layout of the reflectance<br />
module that is positioned over the X,Y<br />
stage is shown in Figure 5.<br />
The 96-spot foil containing the<br />
samples was taped to a metal plate that<br />
mounted in the automated X,Y stage. A<br />
spectrum from a well with no sample<br />
was acquired as a background. Spectra<br />
were then automatically acquired<br />
from the original samples. Figure 6<br />
shows the screen after the software has<br />
acquired the data. The color of each<br />
well in the schematic in the upper left<br />
corresponds to the magnitude (result)<br />
of the chemometric analysis selected.<br />
This could be as simple as the intensity<br />
of the amide band from the protein,<br />
the similarity to a target spectrum, or<br />
the amount of lipid in the sample. In<br />
this case, the color corresponds to the<br />
amount of lipid in the sample based on<br />
this implementation of the Pistorius<br />
method (7). The wells colored red or<br />
orange correspond to samples containing<br />
more lipid material.<br />
Conclusions<br />
Many of the FT-IR techniques that<br />
have been reported for classifying<br />
and characterizing clinical samples<br />
can be applied to analyzing materials<br />
developed for use in biofuels. In<br />
this feasibility study spectra from<br />
algae samples were obtained using<br />
a number of different infrared sampling<br />
techniques, forming a basis for<br />
developing rapid screening methods<br />
to determine the lipid content of<br />
microbiological species intended for<br />
biofuels. These techniques would<br />
prove valuable during several steps<br />
in the development process including<br />
optimizing the algae strains through<br />
the actual production of biomass to<br />
ensure that the algae species are remaining<br />
true and are not contaminated<br />
by wild organisms.<br />
For a small number of samples,<br />
ATR spectroscopy provides an easy<br />
nondestructive way to quickly determine<br />
the chemical composition of<br />
dried samples. For applications with<br />
a large number of samples, the use<br />
of a “well plate” based on the microporous<br />
membrane would provide a<br />
low-cost way to rapidly analyze multiple<br />
samples. Multivariate statistical<br />
techniques could be employed to<br />
eliminate interference from the spectral<br />
features because of the polymer<br />
film, which might otherwise limit<br />
its general use. One interesting possibility<br />
of using a microporous film<br />
as the sample substrate is filtering<br />
samples directly onto the substrate<br />
using an automated 96-sample filtering<br />
system.<br />
The robust nature and relatively<br />
low cost of silicon make it an excellent<br />
choice as a substrate for a 96-<br />
well plate. Transmission sampling<br />
plates can be produced from a single<br />
piece of silicon (120 × 85 mm)<br />
with 96 sample positions or a plate<br />
that mounts 96 individual disposable<br />
windows. The results of the reflectance<br />
analysis using the Array<br />
Automation system are also very<br />
promising, and this appears to be an<br />
easy method for analyzing multiple<br />
samples. As with any analytical application,<br />
the best method depends<br />
on the details of the analysis. However,<br />
FT-IR spectroscopy has the<br />
flexibility and specificity to deliver<br />
a robust solution optimized to the<br />
specific problem.<br />
References<br />
(1) J. Sheehan, T. Dunahay, J. Benemann,<br />
and P. Roessler, “A Look Back at the<br />
U.S. Department of Energy’s Aquatic<br />
Species Program-Biodiesel from<br />
Algae”, NREL/TP-580–24190 (1998).<br />
(2) S.R. Lowry, Cellular and Molecular<br />
Biology 44, 169–177 (1998).<br />
(3) D. Naumann, D. Helm, and H. Labischinski,<br />
Nature 351, 81–82 (1991).<br />
(4) K. Stehfest, J. Toepel, and C. Wilhelm,<br />
Plant Physiology and Biochemistry<br />
43, 717–726 (2005).<br />
(5) A.P. Dean, M.C. Martin, and D.C.<br />
Sigee, Phycologia 46, 151–159<br />
(2005).<br />
(6) D.L. Wetzel, A.J. Eilert, L.N. Pietrzak,<br />
S.S. Miller, and J.A. Sweat, Cellular<br />
and Molecular Biology 44, 145–168<br />
(1998).<br />
(7) A.M. Pistorius, W.J. DeGrip, and T.A.<br />
Egorova-Zachernyuk, Biotechnology<br />
and Bioengineering 103, 123–129<br />
(2009).<br />
(8) M.M. Mossoba, F.M Khambaty, and<br />
F.S. Fry, Applied <strong>Spectroscopy</strong> 56,<br />
732–736 (2002).<br />
Steve Lowry is Application<br />
Scientist, Molecular <strong>Spectroscopy</strong>, with<br />
Thermo Fisher Scientific, Waltham,<br />
Massachusetts. ◾<br />
For more information on this topic,<br />
please visit our homepage at:<br />
www.spectroscopyonline.com
2012<br />
Photonics<br />
West<br />
21–26 January 2012<br />
Call for Papers<br />
Submit your abstract<br />
by 11 July 2011<br />
Applications of optoelectronics, lasers,<br />
micro/nanophotonics, and biomedical optics<br />
Location<br />
The Moscone Center<br />
San Francisco, California, USA<br />
spie.org/pw<br />
Conference dates<br />
21–26 January 2012<br />
Exhibition dates<br />
BiOS: 21–22 January<br />
Photonics West:<br />
24–26 January<br />
Technologies<br />
- BiOS–Biomedical Optics<br />
- OPTO–Integrated Optoelectronics<br />
- LASE–Lasers and Applications<br />
- MOEMS-MEMS–Micro & Nanofabrication<br />
- Green Photonics
38 <strong>Spectroscopy</strong> 26(6) June 2011<br />
www.spectroscopyonline.com<br />
The pH Dependence of the<br />
SERS Spectra of Methyl Yellow<br />
in Silver Colloid<br />
Methyl yellow is an important azo dye that may be used as a pH indicator. In this study, the<br />
surface-enhanced Raman spectra of methyl yellow in silver colloids with various pH values were<br />
investigated. A relative intensity analysis indicated the intensities of the Raman bands changed<br />
primarily when the pH was lowered from 4 to 3. The enhancement of surface-enhanced Raman<br />
scattering (SERS) signals is determined mainly by surface plasmon resonance, charge-transfer<br />
resonance, and their combination. The varying intensities of SERS signals in solutions with different<br />
pH levels may result from the change in the contributions of their combined systems, such as<br />
the charge of methyl yellow molecules and the adsorption of molecules on the surface of silver.<br />
Zhen Long Zhang, Da Hu Chang, and Yu Jun Mo<br />
Surface-enhanced Raman scattering (SERS) is a highly<br />
sensitive analytical tool for investing the adsorption of<br />
molecules and characterizing the structure and orientation<br />
of the molecules on rough metal surfaces (1–5). It is well<br />
known that some combination of three resonances (surface<br />
plasmon resonance, molecular resonance, and charge-transfer<br />
resonance) is responsible for the SERS enhancement (6). Surface<br />
plasmon resonance is mostly a property of the metal, such as<br />
the nature of the conduction band and nanoscale surface features,<br />
whereas molecular resonance is a property of the molecule.<br />
Charge-transfer resonance results from interaction between the<br />
molecule and the rough metal surface (7,8). Some information<br />
about the molecules may be obtained by analyzing the SERS<br />
spectra. Raman shift and relative intensity changes in the SERS<br />
spectra provide information about the adsorption of molecules<br />
on the metal surface (9,10).<br />
Azo dyes have attracted much attention in recent years (11–13),<br />
because they represent the largest class of dyes used in industry<br />
and are widely applied in analytical chemistry as acid–base,<br />
redox, and metallochromic indicators (14). Methyl yellow is an<br />
important azo dye and may be used as a pH indicator. Methyl<br />
yellow presents as the azo form (Figure 1a) in the organic phase,<br />
and as the hydrazo form (MYH + , Figure 1b) in the acidified aqueous<br />
phase. That structure transformation has been studied by the<br />
UV–vis spectrum and resonance Raman spectra (15). In those<br />
studies, however, the Raman spectra were observed only in a<br />
higher wavenumber range, 1100–1650 cm -1 . Moreover, there have<br />
been few systemic investigations of the methyl yellow structure<br />
transformation with variations in pH. In this study, the methyl<br />
yellow structure transformation in solutions with varied pH values<br />
was investigated by SERS. The structure transformation and<br />
adsorption of the methyl yellow molecule on a silver surface were<br />
studied by analyzing the relative intensity change in the Raman<br />
bands in the SERS spectra.<br />
<strong>Experimental</strong><br />
Methyl yellow was purchased from Aldrich Chemical Company<br />
(St. Louis, Missouri). All the chemicals used in the experiments<br />
were analytical grade.<br />
Silver colloids were prepared in an aqueous solution by the<br />
reduction of silver nitrate with sodium citrate following the<br />
method reported by Lee and Meisel (16). Transmission electron<br />
microscopy (TEM) examination of the silver particles revealed<br />
that the particles were homogeneous, with an average diameter<br />
of ~50 nm (17).<br />
The silver colloid was diluted with water in a ratio of 1:4<br />
(v/v). The silver colloid solution was activated by the addition<br />
of 0.01 M NaCl solution to the colloid solution in a ratio of<br />
1:5 (v/v). For SERS measurements, samples were prepared by<br />
incubating the methyl yellow solution (in ethanol) at a concentration<br />
of 5 × 10 -4 M with the NaCl-activated silver colloid at<br />
a ratio of 1:9, resulting in a final concentration of 5 × 10 -5 M.<br />
Diluted HCl was used to adjust the solution pH and pH paper<br />
was used to measure values.
www.spectroscopyonline.com June 2011 <strong>Spectroscopy</strong> 26(6) 39<br />
Raman and SERS spectra were recorded<br />
with a Raman microscopic spectrometer<br />
(Renishaw RM-1000, New Mills, United<br />
Kingdom) composed of an optical microscope,<br />
a CCD video camera, and a spectrometer.<br />
A 632.8-nm HeNe laser was<br />
used as the excitation source. The SERS<br />
spectra of the probed molecules were measured<br />
with an accumulation time of 10 s<br />
using a 20× object lens. The laser power<br />
focused on the sample was ~5 mW, and the<br />
spectral resolution was set to 3 cm -1 . The<br />
analysis of the spectra for all pH values<br />
was performed by nonlinear curve fitting<br />
using Origin 7.0 software (OriginLab Corporation,<br />
Northampton, Massachusetts).<br />
Curve fitting was carried out considering<br />
the band as a Lorentzian curve.<br />
(a)<br />
(b)<br />
Results and Discussion<br />
Figure 2a shows the UV–vis absorption<br />
spectrum of the silver solution. The silver<br />
solution absorbs light at λ max<br />
= 432 nm.<br />
The absorption spectrum of methyl yellow<br />
solution (in ethanol) is shown in Figure<br />
2b. The absorption peak appears at λ max<br />
= 403 nm, which is near the absorption<br />
peak of the silver solution. Figure 2c shows<br />
the absorption spectrum of the combined<br />
system of silver solution and methyl yellow.<br />
The addition of methyl yellow to the<br />
silver solution resulted in a decreased intensity<br />
of the absorption peak, along with<br />
an appearance of a new wide band in the<br />
range of 600–800 nm resulting from the<br />
aggregated silver particles. It was found<br />
that a significant enhancement of the band<br />
intensities may be obtained when aggregates<br />
of two or more nanoparticles oscillate<br />
collectively and these collective oscillations<br />
of nanoparticles extend the range<br />
of useful localized surface plasmon effects<br />
throughout the visible and near-infrared<br />
region of the spectrum (6). The excitation<br />
wavelength of the laser, 632.8 nm, is far<br />
away from the absorption peak of methyl<br />
yellow, thus there are no surface-enhanced<br />
Raman resonance scattering components<br />
in the SERS spectra in this study. The contribution<br />
of molecular resonance to the<br />
SERS enhancement is small.<br />
Figure 3 shows the normal Raman<br />
spectrum of methyl yellow powder. Figures<br />
4 and 5 show the SERS spectra of<br />
methyl yellow in silver colloid solution<br />
with varied pH values. We have recorded<br />
SERS spectra of methyl yellow by changing<br />
the pH values in one-unit increments<br />
from 1 to 7. However, in Figures 4 and 5<br />
we have shown a few characteristic spectra.<br />
The Raman bands are labeled and the<br />
assignments of the Raman bands are listed<br />
in Table I (15,18–23).<br />
Compared with the normal Raman<br />
spectrum, the Raman signals of the molecules<br />
have been significantly enhanced<br />
in SERS. Some new bands appear in the<br />
SERS spectra, including bands at 892,<br />
997, 428, 474, 510, and 977 cm -1 (Table I).<br />
According to a unified approach to SERS<br />
(6), the presence of non-totally symmetric<br />
bands in the excitation profile indicates the<br />
presence of charge-transfer contributions<br />
to the enhancement. Although these molecules<br />
do not have enough symmetry for<br />
a definitive test of the strong changes in<br />
N<br />
N<br />
N<br />
H<br />
N<br />
Figure 1: Schematic structure of methyl yellow as (a) the azo-form in organic phase and as (b) the<br />
hydrazo-form in acidified aqueous phase.<br />
Absorbance (a.u)<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
N<br />
N<br />
CH 3<br />
CH 3<br />
CH 3<br />
CH 3<br />
(b)<br />
(a)<br />
0.0<br />
300 400 500 600 700 800<br />
Wavelength (nm)<br />
Figure 2: UV–vis absorption spectra of (a) silver solution, (b) methyl yellow solution, and (c) the<br />
combined system of silver solution and methyl yellow.<br />
(c)<br />
spectral lines, the presence of the Raman<br />
lines mentioned above in the SERS spectra<br />
indicates strong charge-transfer effects between<br />
the molecules and the silver surface.<br />
When the pH levels are varied from 4 to<br />
7, no new Raman bands appear in the SERS<br />
spectra. At pH 2 and pH 3, however, new<br />
Raman bands appear at 892 cm -1 (Figure<br />
4a), 979 cm -1 (Figure 4b), 1222 cm -1 (Figure<br />
5a), and 1492 cm -1 (Figure 5a). Although the<br />
assignments of these bands are not clear, the<br />
presence of the bands could be attributed<br />
to the vibrational modes of hydrazo form<br />
(MYH + ). MYH + is dominant when the pH<br />
of the solution is less than 3.3, the pK a<br />
of<br />
methyl yellow. The characteristic Raman<br />
bands of MYH + , 1619 and 1174 cm -1 , were<br />
observed (Figure 5a) and are attributed to<br />
υ(C=C) and υ(N-N), respectively (18).
40 <strong>Spectroscopy</strong> 26(6) June 2011<br />
www.spectroscopyonline.com<br />
(a)<br />
1.6<br />
(d)<br />
6<br />
921<br />
Intensity (a.u)<br />
1.2<br />
0.8<br />
0.4<br />
426<br />
515<br />
614<br />
732<br />
828<br />
Intensity (a.u)<br />
4<br />
2<br />
275<br />
427<br />
472<br />
512<br />
542<br />
585<br />
623<br />
728<br />
768<br />
824<br />
1000<br />
(b)<br />
Intensity (a.u)<br />
0.0<br />
80<br />
60<br />
40<br />
20<br />
1000<br />
1138<br />
400<br />
1195<br />
1311<br />
1365<br />
600 800<br />
Raman shift (cm -1 )<br />
0<br />
1000 1200 1400 1600 1800<br />
The relative intensity changes of all the SERS Raman bands<br />
with pH variation were analyzed. Figure 6 shows the relative intensity<br />
variations of three representative SERS bands at 1140, 1408,<br />
and 824 cm -1 with pH variations from 2 to 7. The intensities of the<br />
SERS Raman bands change slightly when the pH values change<br />
from 4 to 7 and from 2 to 3, respectively, whereas there is a large<br />
change in the intensities when the pH value is lowered from 4 to 3.<br />
The azo form predominates when the pH is greater than 3.3,<br />
the pK a<br />
of methyl yellow, and the hydrazo form predominates<br />
when the pH is lower than 3.3. This can be seen clearly by comparing<br />
the SERS from pH 2 to pH 7. A band is present at 276 cm -1<br />
at pH 4 (Figure 4c) and 275 cm -1 at pH 7 (Figure 4d), whereas this<br />
band disappears at pH 2 (Figure 4a) and pH 3 (Figure 4b). It is<br />
reported that Ag-N vibration appears at very close frequencies in<br />
this range (21–23). It is reasonable to think that the methyl yellow<br />
molecule in azo form at high pH levels is adsorbed on the silver<br />
surface through the nonbonding electron of the N atom. On the<br />
other hand, at low pH levels, the dominant structure of methyl<br />
yellow is the hydrazo form, with a positively charged N atom, and<br />
there are more chlorinated sites on the silver surface as a result<br />
of the high Cl - concentration. It is reasonable to suppose that the<br />
1408<br />
1418<br />
1442 1462<br />
1584<br />
1582<br />
Raman shift (cm -1 )<br />
Figure 3: Normal Raman spectrum of methyl yellow powder in the<br />
ranges of (a) 200–950 cm -1 and (b) 950–1800 cm -1 .<br />
(c)<br />
Intensity (a.u)<br />
(b)<br />
Intensity (a.u)<br />
(a)<br />
Intensity (a.u)<br />
0<br />
6<br />
4<br />
2<br />
0<br />
1<br />
0<br />
1<br />
276<br />
322<br />
511 542<br />
582<br />
623<br />
727<br />
768<br />
424<br />
471<br />
824<br />
921<br />
978 1000<br />
428<br />
429<br />
474<br />
473<br />
510<br />
512<br />
528<br />
543<br />
583<br />
626<br />
625<br />
726<br />
726<br />
824<br />
892<br />
923<br />
977 999<br />
0<br />
200 400 600 800 1000<br />
MYH + molecule is adsorbed on the silver surface through the<br />
bridge of N + -Cl - -Ag + .<br />
The Raman spectra provide vibrational information that is<br />
specific for the chemical bonds in molecules. The enhancement<br />
of SERS signals is determined by the surface plasmon resonance,<br />
molecular resonance, charge-transfer resonance, and their combi-<br />
824<br />
Raman shift (cm -1 )<br />
Figure 4: SERS spectra of methyl yellow (5 × 10 -5 M) in 200–1100 cm -1<br />
range at pH (a) 2, (b) 3, (c) 4, and (d) 7.<br />
921<br />
1000
www.spectroscopyonline.com June 2011 <strong>Spectroscopy</strong> 26(6) 41<br />
Table I: Observed normal Raman and SERS bands of DAB in varied environments and their tentative assignments<br />
NRS<br />
(cm -1 )<br />
SERS (cm -1 )<br />
pH 2 pH 3 pH 4 pH 7<br />
1592 1619 1619 1619 1619<br />
1584 1596 1597 1598 1598<br />
1492<br />
1462 1463 1462 1463 1463<br />
1442 1442 1441 1441 1441<br />
Tentative<br />
Assignment<br />
υ(C=C)<br />
(MYH + )<br />
υ(C-C)<br />
υ(C Ph<br />
-N Me<br />
)<br />
δ(C-C)<br />
υ(C-C)<br />
δ(C-N)<br />
δ(C-C)<br />
δ(C-H)<br />
υ(C-C)<br />
δ(C-H) Me<br />
δ(C-N)<br />
References<br />
1418 υ(N=N)<br />
τ(C-N) Me<br />
15,18<br />
1408 1408 1406 1407 1407<br />
1365 1370 1368 1368 1368 υ(C-C) 20<br />
1311 1310 1310 1311 1310<br />
1222<br />
1195 1191 1193 1195 1195<br />
1174<br />
1138 1140 1140 1140 1140<br />
1000 999 1000 1000 1000<br />
977 978<br />
923 921 921 921<br />
892<br />
821 824 824 824 824<br />
768 768<br />
732 726 726 727 728<br />
υ(C-C)<br />
δ(C-N)<br />
δ(C-H)<br />
υ(C-C)<br />
δ(C-H)<br />
υ(N-N)<br />
(MYH + )<br />
υ(C-N)<br />
υ(C-C)<br />
δ(C-C)<br />
δ(C-C)<br />
υ(C-C)<br />
υ(C-C)<br />
δ(C-C)<br />
δ(N=N)<br />
τ(C-C)<br />
γ(C-H)<br />
τ(C-N) Me<br />
τ(C-C)<br />
γ(C-H)<br />
18,19<br />
20<br />
20<br />
20<br />
20<br />
20<br />
18,19<br />
20<br />
20<br />
20<br />
20<br />
20<br />
δ(C-C)<br />
υ(C-C)<br />
δ(C-N)<br />
υ(C-N) Me<br />
20<br />
614 626 625 623 623 δ(C-C) 20<br />
583 582 585<br />
528 543 542 542<br />
515 510 512 511 512<br />
τ(C-C)<br />
γ(C-H)<br />
τ(C-C)<br />
γ(C-H)<br />
474 473 471 472 τ(C-C) 20<br />
426 428 429 424 427 τ(C-C) 20<br />
322<br />
Note: υ, stretch; δ, in-plane bend; γ, out-of-plane bend; τ, torsion<br />
276 275 υ(Ag-N) 21–23<br />
20<br />
20
42 <strong>Spectroscopy</strong> 26(6) June 2011<br />
www.spectroscopyonline.com<br />
(d)<br />
Intensity (a.u)<br />
60<br />
40<br />
20<br />
0<br />
(c)<br />
60<br />
Intensity (a.u)<br />
(b)<br />
Intensity (a.u)<br />
(a)<br />
Intensity (a.u)<br />
40<br />
20<br />
0<br />
12<br />
8<br />
4<br />
0<br />
12<br />
8<br />
4<br />
0<br />
1140<br />
1140<br />
1140<br />
1140<br />
1195<br />
1195<br />
1193<br />
1174<br />
1191<br />
1222<br />
1310<br />
1311<br />
1310<br />
1310<br />
1368<br />
1368<br />
1368<br />
1370<br />
1407<br />
1406<br />
1408<br />
1441<br />
1463<br />
1407<br />
1441<br />
nation (6). The UV–vis absorption spectra<br />
shown in Figure 2 indicate that the contribution<br />
of molecular resonance to the SERS<br />
is small. The surface plasmon resonance is<br />
excited by laser radiation and may result<br />
from the aggregations of silver nanoscale<br />
particles. Some new lines appear in the<br />
SERS spectra, indicating strong chargetransfer<br />
effects between the molecules and<br />
the silver surface. Therefore, the enhancement<br />
of SERS signals is determined mainly<br />
by surface plasmon resonance, chargetransfer<br />
resonance, and their combination.<br />
The change in SERS intensities with<br />
variations in the pH may result from the<br />
change in the contributions of the various<br />
resonances. At high pH levels (pH 4–7), the<br />
azo form of methyl yellow molecules predominates,<br />
because these molecules adsorb<br />
onto the silver surface through Ag-N bonding.<br />
At low pH levels (pH 2–3), the hydrazo<br />
form predominates, because these molecules<br />
are adsorbed on silver surface through<br />
the bridge of N + -Cl - -Ag + . The adsorption<br />
1463<br />
1441<br />
1462<br />
1442<br />
1463<br />
1492<br />
1598<br />
1619<br />
1598<br />
1619<br />
1597<br />
1619<br />
1596<br />
1619<br />
1200 1400 1600 1800<br />
Raman shift (cm -1 )<br />
Figure 5: SERS spectra of methyl yellow (5 ×<br />
10 -5 M) in 1100–1800 cm -1 range at pH (a) 2,<br />
(b) 3, (c) 4, and (d) 7.<br />
Intensity (a.u)<br />
change of the molecules may make the molecular<br />
orientation change, thus causing the<br />
intensities to change. This is consistent with<br />
the surface selection rules based on surface<br />
plasmon resonance (6). The interaction of<br />
molecules with a silver surface may change<br />
primarily as a result of the charge of the<br />
methyl yellow molecule (MYH + ).<br />
Conclusion<br />
The SERS spectra of methyl yellow in<br />
varied pH solutions were studied. The enhancement<br />
of SERS signals is determined<br />
mainly by surface plasmon resonance,<br />
charge-transfer resonance, and their<br />
combination. A relative intensity analysis<br />
of the Raman bands indicated that the<br />
intensities change primarily when the pH<br />
changes from 4 to 3. This may be a result<br />
of a change in the contributions of their<br />
combined system, such as the charge of<br />
methyl yellow molecules and adsorption<br />
of molecules on the silver surface.<br />
References<br />
(1) M. Fleischman, P.J. Hendra, and A.J. McQuillian,<br />
Chem. Phys. Lett. 26, 163–166 (1974).<br />
(2) K. Kneipp, H. Kneipp, V.B. Kartha, R. Manoharan,<br />
G. Deinum, I. Itzkan, R.R. Dasari, and<br />
M.S. Feld, Phys. Rev. E 57, R6281–R6284<br />
(1998).<br />
(3) S. Nie, and S.R. Emory, Science 275, 1102–1106<br />
(1997).<br />
(a) (b) (c)<br />
1800<br />
1200<br />
600<br />
0<br />
(4) A. Sackmann and A. Materny, J. Raman Spectrosc.<br />
37, 305–310 (2006).<br />
(5) P.W. Barber, R.K. Chang, and H. Massoudi, Phys.<br />
Rev. Lett. 50, 997–1000 (1983).<br />
(6) J.R. Lombardi and R.L. Birke, J. Phys. Chem. C<br />
112, 5605–5617 (2008).<br />
(7) J.R. Lombardi, R.L. Brike, T. Lu, and J. Xu, J. Chem.<br />
Phys. 84, 4174–4180 (1986).<br />
(8) J.F. Arenas, I. Lopez Tacon, M.S. Wooley, J. Cotero,<br />
and J.I. Marcos, J. Raman Spectrosc. 29,<br />
673–678 (1998).<br />
300<br />
200<br />
100<br />
0<br />
0<br />
2 3 4 5 6 7 2 3 4 5 6 7 2 3 4 5 6 7<br />
pH<br />
Figure 6: Relative intensity variation of methyl yellow SERS bands at (a) 1140, (b) 1408, and (c)<br />
824 cm -1 with pH variation from 2 to 7.<br />
(9) A.K. Ojha, A. Singha, S. Dasgupta, R.K. Singh,<br />
pH<br />
and A. Roy, Chem. Phys. Lett. 431, 121–126<br />
(2006).<br />
(10) A.K. Ojha, Chem. Phys. 340, 69–78 (2007).<br />
(11) L. Wang, X.J. Pan, and F. Wang, Dyes and Pigments<br />
76, 636–645 (2008).<br />
(12) F.A. Pasha, M. Muddassar, H.W. Chung, S.J. Cho,<br />
and H. Cho, J. Mol. Model. 14, 293–302 (2008).<br />
(13) H. Destaillats, A.G. Turjanski, D.A. Estrin, and<br />
M.R. Hoffmann, J. Phys. Org. Chem. 15, 287–<br />
292 (2002).<br />
50<br />
40<br />
30<br />
20<br />
10<br />
(14) H. Zollinger, Color Chemistry, Syntheses, Properties,<br />
and Applications of Organic Dyes and Pigments<br />
(VCH, New York, 1987), pp.1436–1451.<br />
(15) F.B. James and B.Y. Ernest, J. Phys. Chem. 85,<br />
1005–1014 (1981).<br />
(16) P.C. Lee and D. Meisel, J. Phys. Chem. 86, 3391–<br />
3395 (1982).<br />
(17) Z.L. Zhang, Y.F. Yin, J.W. Jiang, and Y.J. Mo, J. Mol.<br />
Stru. 920, 297–300 (2009).<br />
(18) M. Michl, B. Vlckova, and P. Mojzes, J. Mol. Stru.<br />
482, 217–223 (1999).<br />
(19) K. Machida, B.K. Kim, Y. Saito, K. Igarashi, and T.<br />
Uno, Bull. Chem. Soc. Jpn. 47, 78–82 (1974).<br />
(20) B. Nandita and U. Siva, J. Phys. Chem. A 104,<br />
2734–2745 (2000).<br />
(21) M.M. Miranda and G. Sbrana, J. Raman Spectrosc.<br />
27, 105–110 (1996).<br />
(22) W.S. Oh, M.S. Kim, and S.W. Suh, J. Raman Spectrosc.<br />
18, 253–258 (1987).<br />
(23) K.A. Bunding, R.L. Birke, and J.R. Lombardi,<br />
Chem. Phys. 54, 115–120 (1980).<br />
Zhen Long Zhang and Yu Jun Mo<br />
are with the School of Physics and Electronics<br />
at Henan University, in Kaifeng, China.<br />
Da Hu Chang is with the Department<br />
of Mathematics and Science at the Luoyang<br />
Institute of Science and Technology, in<br />
Luoyang, China. ◾<br />
pH<br />
For more information on this topic,<br />
please visit our homepage at:<br />
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Atomic <strong>Spectroscopy</strong><br />
Determination of Hg in Environmental Samples Using a Direct<br />
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Johan Nortje, Milestone Inc.<br />
As emphasis is continually being placed on the monitoring<br />
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<strong>Experimental</strong><br />
Determine mercury content at various concentrations in environmental<br />
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2709 San Joaquin Soil, a matrix-matched standard reference material<br />
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A direct mercury analyzer, as referenced in EPA Method 7473, incorporates<br />
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Figure 1: Principles of operation of direct mercury analyzer<br />
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with the certified value. Discrepancy on the soil samples can be<br />
attributed to sample homogeneity, and possibly analytical errors,<br />
during the sample preparation step for CVAA analysis.<br />
Table I: Unknown Environmental Samples on DMA-80 vs.<br />
Contract Laboratory (Using CVAA)*<br />
Sample DMA-80 Conc. (µg/kg) CVAA Conc. (µg.kg)<br />
200 ppt standard 0.21<br />
1 ppb standard 0.91<br />
5 ppb standard 4.72<br />
Soil 5.09 5<br />
Soil 0.54 0.63<br />
LCS (5 ppb) 5.54 n/a<br />
Soil 398.01 520<br />
Soil 603.39 1000<br />
Soil 3282.22 2000<br />
Soil 7684.28 6590<br />
*Samples provided by an independent contract laboratory.<br />
Results<br />
See Table I.<br />
Discussion and Conclusion<br />
The DMA-80 successfully processed the environmental and powdered<br />
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obtained on the DMA-80 were in excellent agreement<br />
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44 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
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According to the company, it offers<br />
guaranteed deuterium background<br />
correction and automatic optical set-up. The device includes an<br />
integrated furnace autosampler for preparing standards and intelligently<br />
diluting over-range samples, and an Ebert optical system.<br />
Thermo Fisher Scientific, Madison, WI; www.thermoscientific.<br />
com/ice3300<br />
LC system<br />
The Agilent 1290 Infinity LC system is<br />
available with the company’s Intelligent<br />
System Emulation Technology (ISET)<br />
feature, which is designed to enable the<br />
LC system to emulate other LC systems<br />
for transfer of methods between LC systems,<br />
regardless of brand. According to<br />
the company, the feature allows users to<br />
emulate other HPLC and UHPLC instruments<br />
with a mouse click. Existing 1290<br />
Infinity LC systems reportedly are fully<br />
compatible with the system emulation<br />
feature and can be upgraded. Agilent<br />
Technologies, Santa Clara, CA; www.agilent.com<br />
Ion-trap LC–MS system<br />
Agilent Technologies’ 500<br />
ion-trap LC–MS system is<br />
designed for MS-MS analysis<br />
of chemicals, food- and<br />
product-safety testing, and<br />
other applications. According<br />
to the company, the instrument<br />
offers MS, MS-MS, and<br />
MS n capabilities, and can be<br />
operated with the company’s<br />
LC products.<br />
Agilent Technologies,<br />
Santa Clara, CA; www.agilent.com<br />
Spectrophotometer technical literature<br />
Schimadzu Scientific Instruments has<br />
completed a brochure, “Measurement of<br />
Transmission and Reflectance of PV Materials<br />
and Cells,” for its UV-vis–NIR spectrophotometers.<br />
According to the company,<br />
the brochure explains the role of the<br />
company’s SolidSpec-3700 and UV-3600<br />
spectrophotometers in the manufacture<br />
of solar cell materials, cells, and modules.<br />
It also offers two application notes detailing<br />
the spectrophotometric analysis of<br />
photovoltaics. Schimadzu Scientific<br />
Instruments, Inc., Columbia, MD;<br />
www.ssi.shimadzu.com
www.spectroscopyonline.com<br />
June 2011 <strong>Spectroscopy</strong> 26(6) 45<br />
Photoluminescence instruments<br />
Hamamatsu Photonics’ Quantaurus<br />
compact instruments are designed<br />
for measuring the properties<br />
of photoluminescent materials.<br />
According to the company, the<br />
Quantaurus-Tau instrument measures<br />
fluorescence lifetimes as<br />
short as 100 ps, and the Quantaurus-QY<br />
instrument performs absolute<br />
measurements and requires<br />
no known reference samples. The<br />
instruments reportedly can be<br />
used to analyze materials in thin film, powder, solid, or liquid form,<br />
and liquid samples can be cooled down to –196 °C. Hamamatsu<br />
Phototonics, Bridgewater, NJ; www.hamamatsu.com<br />
Scientific-grade ICCDs<br />
Andor Technology’s iStar scientific-grade<br />
ICCDs are designed to combine rapid<br />
acquisitions rates and ultrahigh sensitivity<br />
down to a single photon. According<br />
to the company, the detectors include<br />
high quantum-efficiency image intensifiers,<br />
thermoelectric cooling to –40 °C,<br />
500-kHz photocathode gating rates, and<br />
enhanced intensifier EBI noise reduction.<br />
The detectors reportedly provide<br />
low jitter, low insertion delay gating electronics and nanosecondscale<br />
optical gating for timing accuracy down to few tens of picoseconds,<br />
allowing precise synchronization of complex experiments<br />
through various input–output triggering options. Andor Technology,<br />
Belfast, Northern Ireland; www.andor.com/istar<br />
Glow discharge OES system<br />
The GD-Profiler 2 RF glow discharge<br />
optical emission spectroscopy system<br />
from Horiba Scientific is designed<br />
to provide ultrafast elemental bulk,<br />
surface, and depth profile analysis.<br />
According to the company, the system<br />
utilizes controlled sputtering of a<br />
material by a 4-mm diameter plasma,<br />
analyzing all elements including gases<br />
(N, O, H, Cl) as a function of the<br />
depth in conductive or nonconductive<br />
layers and substrates. Samples of<br />
varying sizes and shapes can be measured.<br />
Horiba Scientific, Edison, NJ;<br />
www.horiba.com<br />
CW DPSS laser<br />
Oxxius’ SLIM-561-300 continuous<br />
wave diode-pumped<br />
solid-state (CW DPSS) laser is<br />
designed with optical characteristics<br />
that reportedly combine<br />
transverse mode (M 2 less<br />
than 1.2) and pointing stability<br />
of less than 10 µrad over 3 °C.<br />
The 300-mW, 561-nm laser can be used in confocal Raman spectroscopy,<br />
SERS, holography, and laser Doppler velocimetry. The laser<br />
is available in an OEM version designed for integration and a “Plug<br />
& Play” CDRH-compliant version for laboratory use. Oxxius Inc.,<br />
Santa Clara, CA; www.oxxius.com<br />
Consumer safety compliance standards<br />
SPEX CertiPrep’s consumer<br />
safety compliance standards are<br />
designed to help comply with<br />
new regulations being enforced<br />
to protect consumers from a<br />
variety of potentially dangerous<br />
chemicals and elements.<br />
According to the company, recent<br />
wordwide regulations restrict<br />
the levels of heavy metals in<br />
consumer products and waste<br />
electronics, as well as a variety of<br />
phthalates in children’s products. SPEC CertiPrep, Metuchen, NJ;<br />
www.spexcertiprep.com<br />
ICP-OES system<br />
PerkinElmer’s Optima 8x00<br />
ICP-OES system is designed<br />
to optimize sample introduction,<br />
enhance plasma<br />
stability, simplify method<br />
development, and reduce<br />
operating costs. The system’s<br />
sample introduction<br />
feature is designed to<br />
generate a constant flow of uniform droplets for stability and detection<br />
limits. Its plasma generator reportedly uses half the argon of<br />
traditional systems, and a camera offers continuous viewing of the<br />
plasma. PerkinElmer, Waltham, MA; www.perkinelmer.com<br />
FT-IR gas analyzer<br />
Thermo Fisher Scientific’s Antaris<br />
Industrial Gas System (IGS) is an<br />
FT-IR gas analyzer based on the<br />
company’s Nicolet 6700 Fouriertransform<br />
interferometer and<br />
provides scan speeds as fast as<br />
5 Hz at 0.5 cm -1 resolution.The<br />
analyzer reportedly is capable<br />
of monitoring dozens of gases<br />
simultaneously while providing<br />
accurate and fast multicomponent<br />
gas analysis. Applications include industrial analyses such as<br />
landfill methane analysis. Precalibrated gas analysis methods are<br />
available. Thermo Fisher Scientific, Madison, WI;<br />
www.thermoscientific.com/igs<br />
Holographic wire grid polarizers<br />
Infrared polarizers from Optometrics<br />
are designed with<br />
submicrometer grid spacing<br />
produced using a holographic<br />
technique. According to the<br />
company, after exposing a<br />
photoresist coated substrate<br />
to monochromatic light, the<br />
resist has a regular sinusoidal<br />
profile, which is vacuum aluminized<br />
at an oblique angle to create an array of parallel conductors.<br />
The polarizers are available with a spacing of 2700 grooves/mm on<br />
ZnSe, CaF 2<br />
, BaF 2<br />
, KRS-5, and germanium. Optometrics, Ayer, MA;<br />
www.optometrics.com
46 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
EDXRF spectrometer<br />
Rigaku’s benchtop energy dispersive<br />
X-ray fluorescence (EDXRF) spectrometer<br />
is designed to work as a compact<br />
elemental analyzer, delivering rapid<br />
quantitative determination of sodium<br />
to uranium in solids, liquids, powders,<br />
and alloys. According to the company,<br />
the spectrometer features an “icondriven”<br />
touch-screen interface, along<br />
with a built-in printer. Options include<br />
fundamental parameters, an automatic<br />
sample changer, a sample spinner, and<br />
helium purge for enhanced light element<br />
sensitivity. Applied Rigaku Technologies, Austin, TX;<br />
www.rigaku.com<br />
Infrared spectrometer<br />
PerkinElmer’s Frontier FT-IR<br />
spectrometer is designed<br />
as a modular and upgradeable<br />
platform for near-,<br />
mid-, and far-infrared<br />
spectroscopic analysis of<br />
samples such as polymers,<br />
chemicals, consumer<br />
goods, and pharmaceuticals.<br />
According to the company,<br />
the instrument’s automated range changing capability allows<br />
the use of multiple techniques, and its optical system allows the<br />
addition of microscopy and imaging systems for detailed materials<br />
analysis. PerkinElmer, Inc., Seer Green, United Kingdom;<br />
www.perkinelmer.com<br />
NIR spectrometers<br />
Avantes’ AvaSpec NIRLine dispersive,<br />
near-infrared spectrometers<br />
are designed to measure long<br />
wavelengths. The instruments<br />
reportedly come with toroidal<br />
focusing mirrors and dynamic dark<br />
correction. According to the company,<br />
the instruments can perform<br />
a variety of applications, including<br />
moisture content measurement,<br />
qualitative and quantitative measurement of volatile organics, plastic<br />
characterization, material identification, and irradiance measurements.<br />
Avantes, Eerbank, The Netherlands; www.avantes.com<br />
ATR accessory<br />
Pike Technologies’ GladiATR<br />
single reflection diamond<br />
ATR accessory reportedly has<br />
expanded temperature control<br />
options that can be configured<br />
for heating to temperatures as<br />
high as 300 °C. According to the<br />
company, the accessory can be<br />
used for high-temperature kinetic<br />
or material degradation studies.<br />
The accessory reportedly operates with the company’s software<br />
and comprises reflective optics and a monolithic diamond for high<br />
throughput across the full mid-IR and far-IR spectral ranges. Pike<br />
Technologies, Madison, WI; www.piketech.com<br />
ICP-MS system<br />
The aurora M90 ICP-MS system from<br />
Bruker Daltonics reportedly combines<br />
the company’s CRI II collision reaction<br />
interface for interference elimination with<br />
the Nitrox 500 accessory to achieve lower<br />
limits of detection on elements such as As<br />
and Se. The system has an ion mirror and<br />
curved-fringe rods designed to provide<br />
high sensitivity (1 million counts/s for 1<br />
µg/L), low background noise, and low<br />
detection limits. According to the company,<br />
the system can be used for environmental,<br />
food, and clinical applications.<br />
Bruker Daltonics, Billerica, MA; www.bdal.com<br />
Raman analyzer<br />
The EZRaman-1-9 portable Raman<br />
analyzer from Enwave Optronics<br />
is designed to minimize fluorescence<br />
and maximize capability<br />
of Raman analysis in difficult-tomeasure<br />
samples. According to the<br />
company, the analyzer’s excitation<br />
wavelength is above 900 nm.<br />
Enwave Optronics, Inc.,<br />
Irvine, CA; www.enwaveopt.com<br />
Mercury analyzer<br />
The Model RA-3000F Gold+ mercury<br />
analyzer from Nippon Instruments<br />
Corporation is designed for EPA<br />
Methods 1631E and 245.7. According<br />
to the company, the instrument simplifies<br />
low to sub-ppt mercury analysis<br />
and reduces reagent consumption<br />
and wastes by as much as 80%.<br />
Nippon Instruments North<br />
America, College Station, TX; www.hg-nic.us<br />
Raman microscope<br />
Renishaw’s inVia Raman microscope<br />
can be used for nondestructive<br />
testing of sperm DNA for assessing<br />
the healthiness of sperm cells. The<br />
instrument can be customized to<br />
integrate optical tweezing, which<br />
enables researchers to immobilize<br />
sperm cells with a tightly focused<br />
laser beam. The resulting Raman spectra contain information about<br />
the vibrations of molecules within the sperm cells and can be used<br />
to assess the state of its DNA. Renishaw, Hoffman Estates, IL;<br />
www.renishaw.com
www.spectroscopyonline.com<br />
June 2011 <strong>Spectroscopy</strong> 26(6) 47<br />
DNA quality control standard<br />
Starna’s DNA quality control<br />
standard is provided in a 1.5-<br />
mL liquid vial that offers the<br />
DNACON 260/280 reference<br />
material in format suitable for<br />
use in drop technology systems.<br />
The vial reportedly is produced<br />
in an ISO 17025 and ISO Guide<br />
34 accredited environment and<br />
provides a NIST-traceable quality<br />
control standard. According to the company, the concentration is<br />
matched for use with ultralow volume and short-pathlength measurement<br />
systems. Applications include DNA purity evaluations in<br />
clinical and bioscience laboratories. Starna Cells, Inc.,<br />
Atascadero, CA; www.starna.com<br />
Topographic Raman imaging<br />
WITec’s True Surface Microscopy<br />
imaging mode is<br />
designed to allow large-area<br />
topographic coordinates from<br />
the profilometer measurement<br />
to be precisely correlated with<br />
the large-area confocal Raman<br />
imaging data. This option<br />
reportedly enables samples<br />
that would normally require<br />
extensive preparation to obtain<br />
a certain surface flatness to be automatically characterized as they<br />
are. According to the company, it allows scan ranges as large as 50<br />
mm × 100 mm with a spatial resolution of 100 nm vertically and<br />
10 µm laterally. WITec GmbH, Ulm, Germany; www.witec.de<br />
Silicon drift detectors<br />
Amptek’s Super silicon drift<br />
detectors are designed for XRF<br />
applications with OEM handheld<br />
instruments and benchtop<br />
analyzers. According to the<br />
company, the detectors have<br />
125-eV FWHM resolution, an<br />
11.2-µs peaking time, and a<br />
P/B of 8200 with an area of 25<br />
mm 2 and a silicon thickness of 500 µm. The detectors reportedly<br />
are contained inside the same TO-8 package and do not require liquid<br />
nitrogen. Amptek Inc., Bedford, MA; www.amptek.com<br />
Immersion probes<br />
Hellma’s immersion probes<br />
are designed for use in fully<br />
automated tablet dissolution<br />
UV–vis analysis. According<br />
to the company, the probes<br />
have custom-built conical<br />
measuring heads and modified<br />
fiber-optic cables with<br />
five different optical path<br />
lengths available. Hellma<br />
USA, Plainview, NY;<br />
www.hellmausa.com<br />
ICP liquid flow monitor<br />
The TruFlo liquid flow monitor<br />
from Glass Expansion is designed<br />
to measure and digitally display<br />
sample flow rates for an ICP-OES<br />
or ICP-MS nebulizer. According<br />
to the company, the monitor can<br />
report when deviation from specified<br />
flow rates occurs or when<br />
problems such as worn pump tubing, a clogged nebulizer, or an<br />
improperly adjusted peristaltic pump occur. The system reportedly<br />
can provide an electronic record of sample flow rates for regulatory<br />
compliance. Glass Expansion, Pocasset, MA; www.geicp.com<br />
EDXRF spectrometer<br />
The EDX-LE spectrometer from Shimadzu<br />
Scientific Instruments is an<br />
energy dispersive X-ray fluorescence<br />
spectrometer designed to screen<br />
elements regulated by RoHS/ELV<br />
directives. According to the company,<br />
the instrument incorporates<br />
automated analysis functions and a<br />
detector that does not require liquid<br />
nitrogen. Users reportedly can customize set-up functions according<br />
to management methods, set threshold values for each material<br />
or element, and change screening judgment according to the input<br />
method used for threshold values. Shimadzu Scientific<br />
Instruments, Columbia, MD; www.ssi.shimadzu.com<br />
X-ray source<br />
Moxtek’s 50-kV monoblock X-ray<br />
source is designed for applications<br />
including handheld, portable,<br />
and benchtop instrumentation.<br />
According to the company,<br />
the source is a battery-operated,<br />
lowpower device that uses passive<br />
air cooling and delivers a<br />
high intensity flux of approximately<br />
2 × 10 11 photons/s/steradian/0.10 µA. The source reportedly<br />
weighs ~350 g and provides a variable energy output up to 50<br />
kV, a maximum beam current of 0.20 mA, and a total power of up<br />
to 4 W. Moxtek, Orem, UT; www.moxtek.com<br />
Raman system for inverted microscopy<br />
The XploRA INV compact analytical<br />
Ramam chemical imaging microscope<br />
from HORIBA Scientific reportedly combines<br />
the automatization features and<br />
small footprint of a standard confocal<br />
Raman microscope with the capabilities<br />
of an inverted microscope for biological<br />
applications such as cell research, cancer<br />
detection, pharmaceutical verification of<br />
intercellular activities, inclusion of microreactors, and incorporation<br />
of AFM units for tip-enhanced Raman spectroscopy. According to<br />
the company, the microscope’s open structure permits the use of<br />
options and add-ons for inverted microscopes, such as micromanipulators,<br />
“optical tweezers,” and specific enclosures for cell applications.<br />
HORIBA Scientific, Edison, NJ; www.horiba.com/scientific
48 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
Calendar of Events<br />
August 2011<br />
11–15 EUROanalysis 2011<br />
Belgrad, Serbia<br />
www.euroanalysis2011.rs/<br />
1–3 The Conference on Small<br />
Molecule Science (CoSMoS) 2011<br />
Chapel Hill, NC<br />
www.cosmoscience.org<br />
1–5 60th Annual Conference on Applications<br />
of X-Ray Analysis (Denver<br />
X-Ray Converence)<br />
Colorado Springs, CO<br />
www.dxcicdd.com<br />
7–11 Microscopy & Microanalysis 2011<br />
Meeting<br />
Nashville, TN<br />
www.microscopy.org/mandm/2011<br />
14–18 ISOS XVI — Sixteenth International<br />
Symposium on Silicon<br />
Chemistry<br />
Hamilton, Canada<br />
www.isos-xvi.org<br />
28 August–1 September 242nd ACS<br />
National Meeting & Exposition<br />
Denver, CO<br />
help@acs.org, portal.acs.org<br />
September 2011<br />
5–8 RAA2011 — 6th International<br />
Congress on the Application of<br />
Raman <strong>Spectroscopy</strong> in Art and<br />
Archaeology<br />
Parma, Italy<br />
www.fis.unipr.it/raa2011/<br />
11–14 MAF 12 — 12th Conference on<br />
Methods and Applications of<br />
Fluorescence<br />
Strasbourg, France<br />
maf12.unistra.fr/<br />
13–16 8th Symposium on the<br />
Practical Application of Mass<br />
Spectrometry in the Biotechnology<br />
Industry<br />
Raleigh, NC<br />
casss.org/displayconvention.<br />
cfm?conventionnbr=9404<br />
26–28 1st International Symposium<br />
on Biophysical Characterization of<br />
Protein Therapeutics<br />
Rockville, MD<br />
casss.org/displayconvention.<br />
cfm?conventionnbr=9404<br />
October 2011<br />
3–7 19th International Solvent Extraction<br />
Conference (ISEC 2011)<br />
Santiago, Chile<br />
www.isec2011.com<br />
8–12 LABTECH2011 — The 2nd International<br />
Laboratory Technology<br />
Conference & Exhibition<br />
Manama, Bahrain<br />
www.lab-tech.info<br />
9–13 13th Symposium on the Practical<br />
Applications for the Analysis<br />
of Proteins, Nucleotides and Small<br />
Molecules<br />
Amelia Island, FL<br />
casss.org/displayconvention.<br />
cfm?conventionnbr=9438<br />
14 New England Conference on Process<br />
Analytical Technology<br />
Bedford, MA<br />
http://necpat.com<br />
30 October–2 November<br />
17th Microoptics Conference (MOC’11)<br />
Sendai, Japan<br />
Microoptics Group, ogura_at_comemoc.<br />
com, www.comemoc.com/topics_e.html<br />
November 2011<br />
14–16 Eastern Analytical Symposium<br />
Somerset, NJ<br />
www.eas.org<br />
December 2011<br />
11–15 International Symposium<br />
on Surface Science — Focusing on<br />
Nano-, Bio-, and Green Technologies<br />
(ISSS-6)<br />
Tokyo, Japan<br />
Prof. Susumu Fukatsu, isss6_at_sssj.org,<br />
www.sssj.org/isss6/<br />
January 2012<br />
8–14 2012 Winter Conference on<br />
Plasma Spectrochemistry<br />
Tucson, AZ<br />
icpinformation.org<br />
21–26 SPIE Photonics West<br />
San Francisco, CA<br />
spie.org/x2584.xml<br />
March 2012<br />
11–16 Pittcon 2012 — Pittsburgh Conference<br />
on Analytical Chemistry and<br />
Applied <strong>Spectroscopy</strong><br />
Orlando, FL<br />
www.pittcon.org<br />
25–29 243rd ACS National Meeting &<br />
Exposition<br />
San Diego, CA<br />
portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_<br />
ARTICLEMAIN&node_id=9&use_sec=false
www.spectroscopyonline.com June 2011 <strong>Spectroscopy</strong> 26(6) 49<br />
Short Courses<br />
August 2011<br />
11–15 Basics in Mass Spectrometry<br />
and Applications in the<br />
1 X-ray Metrology / Centennial Pharmaceutical Industry<br />
Colorado Springs, CO<br />
(at EUROanalysis 16)<br />
www.dxcicdd.com<br />
Belgrade, Serbia<br />
www.euroanalysis2011.rs/short-courses<br />
2 Fundamentals of Digital Signal<br />
Processing and X-ray Detectors/<br />
Gold Camp<br />
Colorado Springs, CO<br />
www.dxcicdd.com<br />
7–11 Advanced Tools in Environmental<br />
Biogeochemistry — Opportunities<br />
and Limitations<br />
Tuebingen, Germany<br />
www.asms.org/<br />
27–28 Introduction to Modern Mass<br />
Spectrometry<br />
Denver, CO<br />
www.proed.acs.org/courses/search_<br />
results.cfm?categoryID=1&sbc=Y<br />
27-28 Infrared Spectral Interpretation:<br />
A Systematic Approach<br />
Denver, CO<br />
www.proed.acs.org/courses/search_<br />
results.cfm?categoryID=1&sbc=Y<br />
27-28 Structure Determination of<br />
Small Molecule Organic Compounds<br />
Using One and Two Dimensional<br />
NMR <strong>Spectroscopy</strong><br />
Denver, CO<br />
www.proed.acs.org/courses/search_<br />
results.cfm?categoryID=1&sbc=Y<br />
September 2011<br />
11–15 Applied <strong>Spectroscopy</strong>:<br />
Structure Elucidation of Organic<br />
Compounds (at EUROanalysis 16)<br />
Belgrade, Serbia<br />
www.euroanalysis2011.rs/short-courses<br />
21–22 Practical Applications of<br />
Mass Spectrometry for Small<br />
Molecules<br />
Boston, MA<br />
Michael Balogh, instructor<br />
http://www.proed.acs.org/courses/<br />
search_results.cfm?categoryID=1&sbc=Y<br />
October 2011<br />
31 Advanced Impedance <strong>Spectroscopy</strong><br />
for Fuel Cells (Electrochemical<br />
Society sponsored short course at<br />
the Fuel Cell Seminar)<br />
Orlando, FL<br />
www.che.ufl.edu/orazem.<br />
Short_Courses.htm<br />
November 2011<br />
14 High-Throughput Drug Analysis<br />
by LC–MS<br />
Somerset, NJ<br />
www.eas.org<br />
14 Hands-on FTIR, NIR and Data<br />
Analysis — What Is the Right Tool to<br />
Solve Your Problem<br />
Somerset, NJ<br />
www.eas.org<br />
14 Introduction to Metabolomics<br />
Somerset, NJ<br />
www.eas.org<br />
14 Introduction to Near-Infrared<br />
<strong>Spectroscopy</strong>: Applications in the<br />
Pharmaceutical and Biotech<br />
Industries<br />
Somerset, NJ<br />
www.eas.org<br />
14 Interpretation of Mass Spectra<br />
with Practical Solutions to<br />
Problems<br />
Somerset, NJ<br />
www.eas.org<br />
14 Practical Introduction to Raman<br />
<strong>Spectroscopy</strong><br />
Somerset, NJ<br />
www.eas.org<br />
14 Impurity and Degradant Identification:<br />
Strategies for Structure<br />
Elucidation via Chromatography,<br />
MS, and NMR<br />
Somerset, NJ<br />
www.eas.org<br />
14–15 LC–MS: Theory, Instruments,<br />
and Applications<br />
Somerset, NJ<br />
www.eas.org<br />
14 Interpretation of Mass Spectra<br />
with Practical Solutions to<br />
Problems<br />
Somerset, NJ<br />
www.eas.org<br />
14–15 Interpretation of Mass<br />
Spectra with Practical Solutions<br />
to Problems<br />
Somerset, NJ<br />
www.eas.org<br />
14–15 Infrared (IR) Spectral Interpretation<br />
I & II<br />
Somerset, NJ<br />
www.eas.org
50 <strong>Spectroscopy</strong> 26(6) June 2011 www.spectroscopyonline.com<br />
®<br />
Showcase<br />
More Raman Less Fluorescence<br />
Enwave Optronics introduces the affordable and powerful<br />
EZRaman-I-9 Portable Raman analyzer with longer<br />
excitation wavelength above 900nm to minimize fluorescence<br />
and maximize your capability for Raman analysis in<br />
difficult-to-measure samples.<br />
Enwave Optronics, Inc., Irvine, CA.<br />
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Pharmaceutical | Tamara Phillips | 440.891.2773<br />
Ad Index<br />
AB Sciex, LLC 29<br />
Agilent Technologies 3, 5<br />
NIPPON INSTRUMENTS<br />
NORTH AMERICA<br />
Need a new<br />
MERCURY ANALYZER?<br />
Nippon Instruments has<br />
mercury analyzers for<br />
most applications.<br />
Contact Us Today!<br />
Toll-Free: 1.877.247.7241<br />
Direct: 979.774.3800<br />
Email: sales@hg-nic.us<br />
Web: www.hg-nic.us<br />
Hamamastu Corp. 19<br />
Harrick Scientific Corp. 13<br />
New Accessory Catalog!<br />
6125 Cottonwood Drive<br />
Madison, WI 53719<br />
608.274.2721<br />
email: sales@piketech.com<br />
www.piketech.com<br />
PerkinElmer 7, 15, 17<br />
Pike Technologies 33, 35, 50<br />
Amptek, Inc 31<br />
Hellma Cells, Inc. 21<br />
Shimadzu Scientific Instruments<br />
CV Tip<br />
Applied Rigaku Technologies 28<br />
Microscopy and Microanalysis 9<br />
SPIE<br />
37, CV3<br />
Avantes BV 50<br />
Milestone, Inc. CV Tip, 43<br />
Starna Cells, Inc. 8<br />
BaySpec, Inc.<br />
CV4<br />
New Era Enterprises, Inc. 50<br />
Thermo Fisher Scientific CV2, 4<br />
Bruker Optics 11<br />
Enwave Optronics, Inc. 50<br />
Nippon Instruments North America 50<br />
Oxxius SA 8
21–25 August 2011<br />
Register Today<br />
Connecting minds for global solutions<br />
The premier optical science and<br />
emerging technologies meeting.<br />
San Diego Convention Center<br />
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spie.org/op<br />
Exhibition dates<br />
23-25 August 2011<br />
Conference dates<br />
21-25 August 2011
Pervasive Spectral Sensing<br />
Full <strong>Spectroscopy</strong> solutions provider<br />
Full Spectral Solutions Provider: real-time, real world<br />
Biomedical and analytical instrumentation professionals have long recognized great potential<br />
for Raman spectroscopic analyzers in many application areas. Until now ruggedized, portable<br />
and handheld dispersive technologies were virtually nonexistent. Instruments were too big, too<br />
expensive, too fragile, and to sophisticated they required highly trained operators for “real-world”<br />
applications use. Recent advances in high volume optical telecom device manufacturing; however,<br />
present a disruptive new picture today.<br />
World’s first Handheld<br />
1064nm Raman Analyzer<br />
Custom 532nm Raman<br />
Spectrometer<br />
FirstGuard Raman<br />
Handheld Analyzer<br />
Xantus -1064 Raman<br />
Handheld Analyzer<br />
MovingLab Raman Microscope<br />
(532, 785, 1064nm) Nomadic Raman Microscope—<br />
SuperGamut UV/VIS/VIR<br />
three wavelength confi guration<br />
RamSpec Benchtop<br />
Raman Instruments<br />
Spectrometer<br />
Nunavut Deep Cooled<br />
Detectors/Cameras<br />
Raman Micro<strong>Spectroscopy</strong><br />
The latest release of BaySpec’s dispersive<br />
Raman microscope family, the<br />
MovingLab features excellent resolution,<br />
long-termreliability, and portable size.<br />
Ideal for:<br />
Validation for the production<br />
of novel drugs<br />
Forensic labs<br />
Fluorescence suppression<br />
Geological/Gemology<br />
Handheld/Portable Raman Analyzers<br />
The FirstGuard brings sample measurements<br />
out of the lab into the field, allowing personnel<br />
to quickly and accurately identify<br />
unknown chemical substances on the spot.<br />
Ideal for identification and use with:<br />
Narcotics & counterfeit street drugs<br />
Explosives & chemical warfare agents<br />
Hazardous materials & chemical spills<br />
Raw material incoming QA<br />
Deep-cooled Camera/Detectors<br />
Lifetime vacuum seal ensures long<br />
life and reliable operation. Deep-cooled<br />
to -55°C<br />
Ideal for identification and use with:<br />
Low light spectroscopy<br />
Raman Micro<strong>Spectroscopy</strong><br />
Retrofit exciting spectrographs<br />
Motion control<br />
For more information contact BaySpec at (408)512-5928 or email to:<br />
info@bayspec.com, and visit our website www.bayspec.com<br />
BaySpec, Inc.<br />
1101 McKay Drive<br />
San Jose, CA 95131 USA<br />
© 2011 BaySpec, Inc. All rights reserved. FirstGuard, Moving Lab, Nunavut, Nomadic, RamSpec,and Xantus and are trademarks of BaySpec, Inc.