GC-FTIR spectroscopy

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. 

GC-Fourier transform infra-red (GC-FTIR) spectroscopy is less frequently used than GC-MS, but involves a similar principle in which the outlet from the column is coupled to an infra-red spectrophotometer. The technique currently suffers from a lack of library spectra, as the IR spectra taken in the vapour phase can be subtly different from condensed-phase spectra or spectra collected using the well-established KBr disc method. 

Methods for identification of amphetamine and methamphetamine in nrine have been employed using GC/Fourier transform IR (GC/FTIR) spectroscopy (104) however these are not widely used. These methods have provided identification of the amphetamines and metabolites at the low picogram levels. Developments in cryogenic sample deposition for GC/FTlR spectroscopy have allowed the highly selective ability of IR spectroscopy to be used for identification and quantification of these drugs. 

Gas chromatography-Fourier transform infrared spectroscopy (gc-ftir)... 

In addition to modem spectroscopic methods ( H nmr spectroscopy, ftir spectroscopy) and chromatographic methods (gc, hplc), HBr titration (29) is suitable for the quantitative analysis of ethyleneimine samples which contain relatively large amounts of ethyleneimine. In this titration, the ethyleneimine ring is opened with excess HBr in glacial acetic acid, and unconsumed HBr is back-titrated against silver nitrate. 

FTIR instrumentation is mature. A typical routine mid-IR spectrometer has KBr optics, best resolution of around 1cm-1, and a room temperature DTGS detector. Noise levels below 0.1 % T peak-to-peak can be achieved in a few seconds. The sample compartment will accommodate a variety of sampling accessories such as those for ATR (attenuated total reflection) and diffuse reflection. At present, IR spectra can be obtained with fast and very fast FTIR interferometers with microscopes, in reflection and microreflection, in diffusion, at very low or very high temperatures, in dilute solutions, etc. Hyphenated IR techniques such as PyFTIR, TG-FTIR, GC-FTIR, HPLC-FTIR and SEC-FTIR (Chapter 7) can simplify many problems and streamline the selection process by doing multiple analyses with one sampling. Solvent absorbance limits flow-through IR spectroscopy cells so as to make them impractical for polymer analysis. Advanced FTIR... 

KBr) databases. Quantitative analysis by GC-FUR is complicated by many uncertainties associated with both the chromatography and spectroscopy [196]. Bulk property detectors (e.g. TCD, FID, etc.) can be used for quantitative analysis when mixture components are known, but provide little structural information for unknown mixture components. Both integrated absorbance and Gram-Schmidt vector methods have been used for the quantitative analysis of mixture components in GC-FTIR. 

In chromatography-FTIR applications, in most instances, IR spectroscopy alone cannot provide unequivocal mixture-component identification. For this reason, chromatography-FTIR results are often combined with retention indices or mass-spectral analysis to improve structure assignments. In GC-FTIR instrumentation the capillary column terminates directly at the light-pipe entrance, and the flow is returned to the GC oven to allow in-line detection by FID or MS. Recently, a multihyphenated system consisting of a GC, combined with a cryostatic interfaced FT1R spectrometer and FID detector, and a mass spectrometer, has been described [197]. Obviously, GC-FTIR-MS is a versatile complex mixture analysis technique that can provide unequivocal and unambiguous compound identification [198,199]. Actually, on-line GC-IR, with... 

Si element ATR-FTIR spectroscopy was used to analyze this residue, and its spectrum, along with the closest library matches, are shown in Figure 41. The absorbance of this residue is low as a consequence of the thin layer present on the plate. This makes matching the sample spectrum with a reference spectrum somewhat difficult. The closest matches extracted from the library interrogated are to ester-based plasticizer materials, which is consistent with a phthalate-plasticized PVC. A more specific identification could have been made with further testing such as subjecting the residue to GC-MS analysis, but the information suggested by the ATR-FTIR analysis was, in this case sufficient. 

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]. 

Other methods for the determination of aromatics in naphtha include a method (ASTM D5580) using a flame ionization detector and methods that use combinations of gas chromatography and Fourier transform infrared spectroscopy (GC-FTIR) (ASTM D5986) and gas chromatography and mass spectrometry (GC-MS) (ASTM D5769). 

Chemical/Physical. Atkinson et al. (2000) studied the gas-phase reaction of 2-pentanone with OH radicals in purified air at 25 °C and 740 mmHg. A relative rate constant of 4.56 x 10 cmVmolecule sec was calculated for this reaction. Reaction products identified by GC, FTIR, and atmospheric pressure ionization tandem mass spectroscopy were (with respective molar yields) were formaldehyde, 1.03 acetaldehyde, 0.51 propanal, 0.19 2,4-pentanedione, 0.12 and molecular weight 147 organic nitrates. 

Consider excerpts 3T-3V. What operational parameters should you report when FTIR spectroscopy is used in your research What parameters should you include when GC is used in your research (If unfamiliar with these techniques, ask your instructor what these parameters mean.)... 

Herres, W. (1987). HRGC-FTIR, Capillary GC, and FTIR Spectroscopy Theory and Applications. New York Huthig. 

Monitoring reaction progress throughout a multistep synthesis is a relatively difficult task.22 Typical methods used for solution-phase synthesis, including thin-layer chromatography (TLC), GC, and most types of mass spectrometry (MS), are less informative for solid-phase methods. However, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) are particularly useful in solid-phase strategies. 

The combination of pyrolysis with GC/FTIR was presented by Davies et al. (2002), who showed that gas chromatography coupled with FTIR spectroscopy can be used as a complementary technique to the conventional GC/MS analysis, by an easier determination of structural isomers (e.g.,p-cresol, m-cresols,p-cresol). 

C/min and secondly a ramp from 100 - 300°C at 20°C/min was used. Injector and detector temperatures were maintained at 270°C and 300°C respectively. GLC-FID/FPD analysis was performed on a Varian 3400 gas chromatograph using the same chromatographic conditions as used in the GC-MS runs. FTIR spectroscopy was performed on a Nicolet instrument using the thin film on sodium chloride plates technique for liquids and the potassium bromide pellet technique for solids. 

Herres, W. (1987). HRGC-FTIR, Capillary GC and FTIR Spectroscopy Theory and Applications. New York Huthig. Mattson, J.S., Ed. (1977). Infrared, Correlation and Fourier Transform Spectroscopy. New York Marcel Dekker. Nakanishi, K., and Solomon, P.H. (1977). Infrared Absorption Spectroscopy-Practical, 2nd ed. San Francisco Holden-Day. Roeges, N.P.G. (1984). Guide to Interpretation of Infrared Spectra of Organic Structures. New York Wiley. 

Various methods and instruments are available for measuring gas concentrations in fire effluents, e.g., gas detector tubes, ion-selective electrodes, GC/MS (gas chromatography/mass spectrometry), and Fourier Transform Infrared (FTIR) spectroscopy. An extensive review of the methods is provided in ASTM E 800 and ISO 19701. 

GC/FTIR Gas Chromatography/Fourier Transform Infrared Spectroscopy... 

M.T. Soderstrom, Identification of VX Type nerve agents using cryodeposition GC-FTIR, in de Haseth (Ed.) Fourier Transform Spectroscopy 11th International Conference, American Institute of Physics, New York, 457-460, 1998. 

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