Experimental - Spectroscopy
Experimental - Spectroscopy
Experimental - Spectroscopy
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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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