Fourier transform infrared, identification

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. 

Analytical investigations may be undertaken to identify the presence of an ABS polymer, characterize the polymer, or identify nonpolymeric ingredients. Fourier transform infrared (ftir) spectroscopy is the method of choice to identify the presence of an ABS polymer and determine the acrylonitrile—butadiene—styrene ratio of the composite polymer (89,90). Confirmation of the presence of mbber domains is achieved by electron microscopy. Comparison with available physical property data serves to increase confidence in the identification or indicate the presence of unexpected stmctural features. Identification of ABS via pyrolysis gas chromatography (91) and dsc ((92) has also been reported. 

The identification of alkanesulfonates is possible by infrared spectroscopy. Computer-supported Fourier transform infrared spectroscopy (FT-IR) allows the... 

The basic methods of the identification and study of matrix-isolated intermediates are infrared (IR), ultraviolet-visible (UV-vis), Raman and electron spin resonance (esr) spectroscopy. The most widely used is IR spectroscopy, which has some significant advantages. One of them is its high information content, and the other lies in the absence of overlapping bands in matrix IR spectra because the peaks are very narrow (about 1 cm ), due to the low temperature and the absence of rotation and interaction between molecules in the matrix. This fact allows the identification of practically all the compounds present, even in multicomponent reaetion mixtures, and the determination of vibrational frequencies of molecules with high accuracy (up to 0.01 cm when Fourier transform infrared spectrometers are used). 

Deveaux M, Huvenne J-P. 1987. Identification of solvents of abuse using gas chromatography/fourier transform infrared spectrometry after headspace sampling. Chromatographia 23 626-630. 

Dixit, V. et al.. Identification and qnantification of industrial grade glycerol adulteration in red wine with Fourier transform infrared spectroscopy using chemometrics and artificial neural networks, Appl. Spectros., 59, 1553, 2005. 

It is only since 1980 that in situ spectroscopic techniques have been developed to obtain identification of the adsorbed intermediates and hence of reliable reaction mechanisms. These new infrared spectroscopic in situ techniques, such as electrochemically modulated infrared reflectance spectroscopy (EMIRS), which uses a dispersive spectrometer, Fourier transform infrared reflectance spectroscopy, or a subtractively normalized interfacial Fourier transform infrared reflectance spectroscopy (SNIFTIRS), have provided definitive proof for the presence of strongly adsorbed species (mainly adsorbed carbon monoxide) acting as catalytic poisons. " " Even though this chapter is not devoted to the description of in situ infrared techniques, it is useful to briefly note the advantages and limitations of such spectroscopic methods. 

Several additional instrumental techniques have also been developed for bacterial characterization. Capillary electrophoresis of bacteria, which requires little sample preparation,42 is possible because most bacteria act as colloidal particles in suspension and can be separated by their electrical charge. Capillary electrophoresis provides information that may be useful for identification. Flow cytometry also can be used to identify and separate individual cells in a mixture.11,42 Infrared spectroscopy has been used to characterize bacteria caught on transparent filters.113 Fourier-transform infrared (FTIR) spectroscopy, with linear discriminant analysis and artificial neural networks, has been adapted for identifying foodbome bacteria25,113 and pathogenic bacteria in the blood.5... 

Helm, D. Labischinski, H. Schallehn, G. Naumann, D. Classification and identification of bacteria by Fourier-transform infrared spectroscopy. J. Gen. Microbiol. 1991,137, 69-79. 

The analytical techniques proposed in the literature generally give reliable information on lipids present in the paint layer. However, the presence of lipid mixtures and of particular environmental conservation conditions may affect the lipid pattern to such an extent that their identification may be very difficult and sometimes erroneous. Thus, a multianalytical approach is recommended which integrates chromatographic data with techniques such as mapping based on Fourier transform infrared spectroscopy or SIM on cross-sections, in order to better understand the distribution of lipids in the various paint layers. 

V.A. Basiuk, Pyrolysis of valine and leucine at 500°C identification of less volatile products using gas chromatography Fourier Transform infrared spectroscopy mass spectrometry, J. 

Chromatographic methods are used to separate the components in a mixture, but in a complex mixture, a single chromatographic method or step many not separate all components. In these cases, using simple retention time to identify the components will not suffice and the identification of components in the mixture will be incorrect. Thus, the addition of a method of identification such as mass spectrometry (MS) or Fourier transform infrared (FTIR) is essential. In some cases, it may even be necessary to confirm either an FTIR or MS identification by the same method applied in a different way. For example, FTIR may be followed by MS, or electron ionization (El) MS followed by chemical ionization (Cl) MS or by an entirely different method. 

Wang, J. A., Sun, S. Q., Zhou, Q., et al. (1999). Nondestructive identification of ballpoint writing inks with Fourier transform infrared microscope. Chinese Journal of Analytical Chemistry 27 697-700. 

Non-ionic surfactants of a commercial washing powder were separated by supercritical fluid chromatography (SFC) and determined by APCI-MS. The constituents were first extracted by supercritical fluid extraction (SFE) using C02 with or without methanol as a modifier. Variations of the conditions resulted in a selective extraction of the analytes, which could be determined without further purification. Six groups of surfactants were observed, four of which are alkyl-polyethoxylates. The presence of APEO could be excluded by identification recording SFC-FTIR (Fourier transform infrared) spectra [31]. 

Structure elucidation of semiochemicals by modern NMR-techniques (including HPLC/NMR) is often hampered by the very small amounts of available material and problems in the isolation of pure compounds from the complex mixtures they are embedded in. Thus, the combination of gas chromatography and mass spectrometry, GC/MS, is frequently the method of choice. Determination of the molecular mass of the target compound (by chemical ionisation) and its atomic composition (by high resolution mass spectrometry) as well as a careful use of MS-Ubraries (mass spectra of beetle pheromones and their fragmentation pattern have been described [27]) and gas chromatographic retention indices will certainly facihtate the identification procedure. In addition, the combination of gas chromatography with Fourier-transform infrared spec-... 

Due to its relatively low sensitivity, the combination of gas chromatography with Fourier transform infrared spectroscopy (GC-FTIR) is not a standard technique in semiochemical research. Nevertheless, it could come in handy for the identification of some compounds with utterly uninformative mass spectra [22]. 

The advent of computers and Fourier transform completely revolutionized the detection and identification of organic compounds. Modern automated instruments allow very small samples in the nanogram (10 g) range to be characterized in a very short time. The application of Fourier transform nuclear magnetic resonance (FTNMR) and Fourier transform infrared (FTIR) allows recovery of the sample in contrast to mass spec-trometric (MS) determination which is a destructive but quite often a necessary technique. 

Kirkwood, J., Al-Khaldi, S. F., Mossoba, M. M., Sedman, J., and Ismail, A. A. (2004). Fourier transform infrared bacteria identification with the use of a focal-plane-array detector and microarray printing. Appl. Spectrosc. 58,1364-1368. 

Rebuffo, C. A., Schmitt, J., Wenning, M., von Stetten, F., and Scherer, S. (2006). Reliable and rapid identification of Listeria monocytogenes and Listeria species by artificial neural network-based Fourier transform infrared spectroscopy. Appl. Environ. Microbiol. 72, 994-1000. 

Thompson, S. E., Foster, N. S., Johnson, T. J., Valentine, N. B., and Amonette, J. E. (2003). Identification of bacterial spores using statistical analysis of Fourier transform infrared photoacoustic spectroscopy data. Appl. Spectrosc. 57, 893-899. 

However, there are limitations to applying this technique to unknown materials. Because the recorded value is mass loss, this is not exactly a unique attribute. However, some interesting developments in combining TGA with other techniques, such as mass spectrometry, fourier transform infrared, or titrators [4,15], have expanded the utility of this technique to the identification of unknown materials. 

For complete identification, relevant direct information on the molecular structure of the analyte is always more specific and hence more reliable than indirect information. Analytical steps based on molecular spectroscopy all provide direct more or less detailed information on the structure of the analyte. This is particularly true for fourier-transform infrared (FTIR) and mass spectroscopy (MS), where the spectra have a very high information content. 

Despite its inherent analytical difficulties, gas chromatography on capillary columns in combination with sensitive and specific mass spectrometry has been widely used for separation of these analytes. Typical examples of such applications are those interfacing gas chromatography with mass spectrometry via electron impact (470, 484, 480, 489), chemical ionization (481, 478, 483, 473), or both interfaces (474, 475, 487, 488). Apart from mass spectrometry, Fourier transform infrared spectrometry has also been suggested as an alternative very useful identification tool in the area of the -agonist analysis. Capillary gas chromatography with Fourier transform infrared spectrometry was successfully employed to monitor clenbuterol, mabuterol, and salbutamol residues in bovine liver and urine (471). 

For qualitative analysis, two detectors that can identify compounds are the mass spectrometer (Section 22-4) and the Fourier transform infrared spectrometer (Section 20-5). A peak can be identified by comparing its spectrum with a library of spectra recorded in a computer. For mass spectral identification, sometimes two prominent peaks are selected in the electron ionization spectrum. The quantitation ion is used for quantitative analysis. The confinnation ion is used for qualitative identification. For example, the confirmation ion might be expected to be 65% as abundant as the quantitation ion. If the observed abundance is not close to 65%, then we suspect that the compound is misidentified. 

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