Gas chromatography/infrared spectroscopy GC/IR

Infrared spectroscopy has been. combined with various other analytical techniques. Gas chromatography-infrared spectroscopy (GC-IR) allows the identification of the components eluting froiti a gas chromatograph. GC-IR has certain advantages over, say, gas chromatography-mass spectrometry (GC-MS). While GC-MS is able to distinguish easily between compounds of different mass, it is unable to differentiate structural isomers of the same molecular mass. By comparison, GC-IR can easily distinguish such isomers. 

Spectrometers are routinely attached to computers that can search for matches between the spectrum of an unknown and a library of known spectra. As with mass spectrometry, gas chromatographs can be attached to IR spectrometers and spectra can be determined as the individual components of a mixture elute from a column. As noted in Section 15.2, this technique is called gas chromatography/infrared spectroscopy, or GC/IR. 

The wide range of spectroscopic techniques such as UV, infrared (IR), Gas Chromatography-Mass Spectroscopy (GC-MS), Liquid Chromatography-Mass spectra (LC-MS), Nuclear Magnetic Resonance (NMR), and mass spectra (MS) form the backbone of modem stmctural elucidation studies as mentioned in the Figure 8.2. Prior to the availability of such advanced techniques, ambiguities existed in the determination of stmctures of bioactive compounds. The process of spectroscopic determination should be closely allied to familiarity with the scientific literature. If the compound has not been described, it may be very similar to reported compounds and that may assist in the interpretation of data for the unknown. In this regard, an awareness of the coextractives from the plant may also be of value to determine the stmctures. 

NMR) [24], and Fourier transform-infrared (FT-IR) spectroscopy [25] are commonly applied methods. Analysis using mass spectrometric (MS) techniques has been achieved with gas chromatography-mass spectrometry (GC-MS), with chemical ionisation (Cl) often more informative than conventional electron impact (El) ionisation [26]. For the qualitative and quantitative characterisation of silicone polyether copolymers in particular, SEC, NMR, and FT-IR have also been demonstrated as useful and informative methods [22] and the application of high-temperature GC and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is also described [5]. 

The analytical data in the OCAD is derived from four different techniques. These are nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), gas chromatography/mass spectrometry (GC/MS), and gas chromatography retention indices (GC(RI)). With a few exceptions, the OCAD contains only data of compounds that are listed in the schedules of the CWC and their derivatives of BSTFA and dimercaptotoluene. 

We can establish the identity of a drug by infrared spectroscopy (IR) or gas chromatography-mass spectrometry (GC-MS). IR provides clues to the functional groups, and it can confirm the structure by comparing the spectrum with that of an authentic sample. 

ENVIRONMENTAL APPLICATIONS OF GAS CHROMATOGRAPHY/FOURIER TRANSFORM INFRARED SPECTROSCOPY (GC/FT-IR), Charles J. Wurrey and Donald F. Gurka... 

Wang, F. Edwards, K (2007). Separation of C2-Naphthalenes by Gas Chromatography x Fourier Transform Infrared Spectroscopy (GC x FT-IR) Two-Dimensional Sepwation Approach. Anal. Chem., Vol.79, pp. 106-112, ISSN 0003-2700. 

Gas chromatography-infrared (GC-IR) spectroscopy is an appropriate technique for drug analysis as it can be used for isomer separation or contaminant detection. Amphetamines are one class of drug that have been successfully differentiated by using GC-IR spectroscopy. Amphetamines are structurally similar molecules that can be easily mis-identified. Although such similar compounds cannot be differentiated by their mass spectra, there are prominent differences... 

Techniques used in thermal degradation studies include controlled pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS), MS, controlled pyrolysis infrared (IR) spectroscopy, differential scanning calorimetry (DSC) and IR spectroscopy. Equipment suppliers are reviewed in Appendix 1. 

Purification was performed by preparative TLC. The compounds obtained were analyzed by Ultraviolet, Infrared and Nuclear Magnetic Resonance spectroscopy and by Gas Chromatography-Mass Spectrometry (GC-MS). The GLC analysis was carried out with a Perkin Elmer mod.990 equipped with a flame ionization detector, on a glass column OV 17 3%. NMR spectra were measured with a Varian 100 MHz for solutions in deuterated chloroform with tetramethyl-silane as internal standard. IR spectra were performed on a Perkin Elmer mod. 157 G in chloroform solution. GLC-MS spectra were carried out with an LKB 9000 at 70 eV. and a glass column OV 17 at 235 C. 

In most respects, the standard approach taken to analyze the fatty acids of functional foods is similar to that for conventional foods. The steps are to extract the total lipids or fatty acids, convert the fatty acids to a suitable derivative (often to fatty acid methyl esters (FAME)), and analyze the derivatized fatty acids by a suitable chromatographic technique, usually GC with flame ionization detection (FID), Other chromatographic techniques, including gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC), may be required. Nonchromatographic techniques such as infrared (IR) spectroscopy may be used in some simations, perhaps because of the speed of analysis. 

Initially, simple methods such as ultraviolet-visible (UV-Vis), fluorescence or infrared (IR) spectroscopy were proposed in order to estimate the total amount of antioxidants in various food samples. However, coupled methods such as gas chromatography-mass spectrometry (GC-MS), high performance liquid chromatography with ultraviolet-visible (HPLC-UV-Vis) or nuclear magnetic resonance detector (HPLC-NMR) and liquid chromatography-mass spectrometry (LC-MS) are employed more to quantify individual tocols or carotens from various corn-based food samples. In this chapter all these methods of analysis will be briefly described. 

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