Experimental - Spectroscopy

32 Spectroscopy 26(6) June 2011 www.spectroscopyonline.com
Figure 1: Selecting the protein spectral region in OMNIC TQ Analyst software.
Absorbance
Absorbance
0.12
0.10
0.08
0.06
0.04
0.02
0.12
0.10
0.08
0.06
0.04
0.02
*Algae powder by ATR
*Algae deposited on foil ATR
3500 3000
based on specific features in the spectra.
The authors emphasized that the
sample preparation is a key step to
2500 2000 1500 1000
Wavenumbers ( cm-1 )
Figure 2: ATR spectra from powdered algae (top) and algae deposited on an aluminum foil
surface (bottom).
obtaining reproducible results. In this
paper, several different infrared sampling
techniques will be described that
can be used to analyze microbiological
samples. The goal of this work was to
identify a cost-effective technique that
might greatly increase the number of
samples that can be analyzed with automated
spectroscopy.
Experimental
Portions of dried samples of different
algae specimens were directly
analyzed by attenuated total reflectance
(ATR) spectroscopy. Aqueous
suspensions of the material were
deposited on various substrates for
both transmittance and reflectance
studies. The actual chemical compositions
of the algae samples available
for this study were unknown.
An analytical method modeled after
the work of Pistorius and colleagues
was created using Thermo Scientific
OMNIC TQ Analyst software
(Thermo Fisher Scientific, Waltham,
Massachusetts).
The key parameters from their
work that were used in this analysis
method are shown in Table I.