Fourier transform infrared detection methods

Chemical Gas Detection. Spectral identification of gases in industrial processing and atmospheric contamination is becoming an important tool for process control and monitoring of air quaUty. The present optical method uses the ftir (Fourier transform infrared) interference spectrometer having high resolution (<1 cm ) capabiUty and excellent sensitivity (few ppb) with the use of cooled MCT (mercury—cadmium—teUuride) (2) detectors. 

The use of detection methods sueh as mass speetrometry (MS) and Fourier-transform infrared (FTIR) speetroseopy ean be very useful with respeet to the quality... 

More sophisticated detection methods for gas chromatography are also employed in the analysis of hydrocarbons gas chromatography-mass spectrometry (EPA 8270C) and gas chromatography-Fourier transform infrared spectroscopy (EPA 8410). These procedures have a significant advantage in providing better characterization of the contaminants and thus are of particular use where some environmental modification of the hydrocarbons has taken place subsequent to soil deposition. 

Grosjean, D E. C. Tuazon, and E. Fujita, Ambient Formic Acid in Southern California Air A Comparison of Two Methods, Fourier Transform Infrared Spectroscopy and Alkaline Trap-Liquid Chromatography with UV Detection, Environ. Sci. Technol., 24, 144-146 (1990). 

FTIR Spectroscopy and Mechanisms on Electrode. The basis of Fourier transform infrared spectroscopy was described in Section 6.2.6. One of the more difficult aspects of detecting the mechanism of electrode reactions is that of knowing the nature of the intermediate radicals on the electrode surface. Infrared spectroscopy measures chemical bonds, so it is an ideal method for detecting which bonds are present and hence which intermediate radicals are taking part in a surface reaction at a given potential, etc. 

Optical methods are based on fluorescence probe-labeled aptamers (fluorescence intensity, fluorescence anisotropy), or label-free aptamers can be used for detection of analyte using SPR or Fourier transform infrared attenuated total reflection (FTIR-ATR). 

In the case of an unknown chemical, or where resonance overlap occurs, it may be necessary to call upon the full arsenal of NMR methods. To confirm a heteronuclear coupling, the normal H NMR spectrum is compared with 1H 19F and/or XH 31 P NMR spectra. After this, and, in particular, where a strong background is present, the various 2-D NMR spectra are recorded. Homonuclear chemical shift correlation experiments such as COSY and TOCSY (or some of their variants) provide information on coupled protons, even networks of protons (1), while the inverse detected heteronuclear correlation experiments such as HMQC and HMQC/TOCSY provide similar information but only for protons coupling to heteronuclei, for example, the pairs 1H-31P and - C. Although interpretation of these data provides abundant information on the molecular structure, the results obtained with other analytical or spectrometric techniques must be taken into account as well. The various methods of MS and gas chromatography/Fourier transform infrared (GC/FTIR) spectroscopy supply complementary information to fully resolve or confirm the structure. Unambiguous identification of an unknown chemical requires consistent results from all spectrometric techniques employed. 

Although not used in any of the overall methods found, Fourier transform-infrared spectroscopy for detection after GC can supplement MS to verify the presence of DNOC in samples (Budzinski et al. 1992 Gurka et al. 1991 Schneider et al. 1991). Alternative separation methods have also been shown to be applicable to nitrophenols, including DNOC, but have not yet become routine. These methods include supercritical fluid chromatography (Ong et al. 1992 Pospisil et al. 1992), capillary zone electrophoresis (Chao and Whang 1994), and micellar electrokinetic chromatography (Ong et al. 1991). 

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