Chromatography GC/IR

All of the infrared experiments were performed on a Digilab FTS-40 Fourier transform infrared (FT-IR) spectrometer equipped with a narrow-band liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector. The spectrometer was operated at a nominal resolution of 4 cm-1 using a mirror velocity of 1.28 cm/s. The data collected using the gas chromatography (GC) IR software were measured at 8 cm-1 resolution. Protein assays for all the experiments were measured on a Beckman DU-70 UV-visible spectrophotometer. 

H NMR, NMR, gas chromatography (GC) IR, and GC MS. The solution of S-monomer at room temperature gave a mixture of the SS-dimer, SSS-trimer, and a polymer (Scheme 38). Evidence for formation of an SSSS-tetramer (M 440) was only obtained by GC MS. Similar results were obtained on FVP of (5-ethyl-2-thiophene-yl)methyl benzoate <1997JOC8980>. 

Table 17.15 shows results obtained from the application of various bulk and surface analysis methods to lithium metal at rest or after cyclization experiments, as well as at noble metal and carbon electrodes after cathodic polarization. Several surface and elemental analysis methods are applied, including X-ray photoelectron spectroscopy (XPS, ESCA/XPS), energy dispersive analysis of X-rays (X-ray microanalysis, EDAX), Eourier transform infrared spectroscopy (ETIR), Auger electron spectroscopy (AES), ellipsometry (E), electro-modulated infrared reflectance spectroscopy (EMIRS), double modulation Fourier transform infrared spectroscopy (DMFTIR), subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS), gas chromatography (GC), IR spectroscopy. X-ray diffraction (XRD), and atomic force microscopy (AFM). 

Tar. Before the development of gas chromatography (gc) and high pressure Hquid chromatography (hplc), the quantitative analyses of tar distillate oils involved tedious high efficiency fractionation and refractionation, followed by identification or estimation of individual components by ir or uv spectroscopy. In the 1990s, the main components of the distillate fractions of coal tars are deterrnined by gc and hplc (54). The analytical procedures included in the specifications for tar bulk products are given in the relevant Standardi2ation of Tar Products Tests Committee (STPTC) (33), ISO (55), and ASTM (35) standards. 

Conductivity detectors, commonly employed in ion chromatography, can be used to determine ionic materials at levels of parts per million (ppm) or parts per bUHon (ppb) in aqueous mobile phases. The infrared (ir) detector is one that may be used in either nonselective or selective detection. Its most common use has been as a detector in size-exclusion chromatography, although it is not limited to sec. The detector is limited to use in systems in which the mobile phase is transparent to the ir wavelength being monitored. It is possible to obtain complete spectra, much as in some gc-ir experiments, if the flow is not very high or can be stopped momentarily. 

In modern times, most analyses are performed on an analytical instrument for, e.g., gas chromatography (GC), high-performance liquid chromatography (HPLC), ultra-violet/visible (UV) or infrared (IR) spectrophotometry, atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry. Each of these instruments has a limitation on the amount of an analyte that they can detect. This limitation can be expressed as the IDL, which may be defined as the smallest amount of an analyte that can be reliably detected or differentiated from the background on an instrument. 

The logical approach to problem solving for rubber analysis at Polysar Ltd was described by Chu [73] (cf. Schemes 2.4 and 2.5). Systematic analysis involves sampling, elimination of interference and measurement. Methods employed include chromatography (GC, HS-GC, HPLC, SEC, IC), spectroscopy (AAS, UV/VIS, IR, NMR), MS, microscopy and thermal analysis. The specific role of each of these techniques for the analysis of rubber compounds with or without... 

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... 

There is a need for increased chromatography-FTIR sensitivity to extend IR analysis to trace mixture components. GC-FTIR-MS was prospected as the method of choice for volatile complex mixture analysis [167]. HPLC-FT1R, SFC-FTIR and TLC-FTIR are not as sensitive as GC-FTIR, but are more appropriate for analyses involving nonvolatile mixture components. Although GC-FTIR is one of the most developed and practised techniques which combine chromatography (GC, SFC, HPLC, SEC, TLC) and FUR, it does not find wide use for polymer/additive analysis, in contrast to HPLC-FTIR. 

The same can be said for the sections concerning the instrumental techniques of GC, IR, NMR, and HPLC. The chromatographic techniques of GC and HPLC are presented as they relate to thin-layer and column chromatography. The spectroscopic techniques depend less on laboratory manipulation and so are presented in terms of similarities to the electronic instrumentation of GC and HPLC techniques (dual detectors, UV detection in HPLC, etc.). For all techniques, the emphasis is on correct sample preparation and correct instrument operation. 

Wilkins CL. Directly-Linked Gas Chromatography-Infrared-Mass Spectrometry (GC/ IR/MS). Published Online 15 AUG 2006. 

We discussed the fundamentals of mass spectrometry in Chapter 10 and infrared spectrometry in Chapter 8. The quadrupole mass spectrometer and the Fourier transform infrared spectrometer have been adapted to and used with GC equipment as detectors with great success. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectrometry (GC-IR) are very powerful tools for qualitative analysis in GC because not only do they give retention time information, but, due to their inherent speed, they are also able to measure and record the mass spectrum or infrared (IR) spectrum of the individual sample components as they elute from the GC column. It is like taking a photograph of each component as it elutes. See Figure 12.14. Coupled with the computer banks of mass and IR spectra, a component s identity is an easy chore for such a detector. It seems the only real... 

There are many analytical techniques available that measure total petroleum hydrocarbon concentrations in the environment, but no single method is satisfactory for measurement of the entire range of petroleum-derived hydrocarbons. In addition, and because the techniques vary in the manner in which hydrocarbons are extracted and detected, each method may be applicable to the measurement of different subsets of the petroleum-derived hydrocarbons present in a sample. The four most commonly used total petroleum hydrocarbon analytical methods include (1) gas chromatography (GC), (2) infrared spectrometry (IR), (3) gravimetric analysis, and (4) immunoassay (Table 7.1) (Miller, 2000, and references cited therein). 

Today, there are many so-called hyphenated methods with IR. These methods include gas chromatography-infrared (GC-IR) where the IR spectra are taken from materials as they are evolved through the column. Related to this are high-performance liquid chromatography-infrared (HPLC-IR), thermogravimetry-infrared (TG-IR), and multispec-tral infrared (MS-IR). 

In terms of coupling flame generation and detection methods, several combinations are common. Generally, shock tubes are coupled with IR and UV absorption and gas chromatography (GC) detectors, while flow reactors are used in tandem with GC, electron spin resonance, and resonance fluorescence detection. 

Content, as well as impurity determinations, are done by chromatographic procedures such as gas chromatography (GC), high pressure liquid chromatography (HPLC) [831], capillary electrophoresis (CE) [832], and by spectroscopic techniques (UV, IR, MS, and NMR) [833, 834]. 

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