Gas chromatography Chapters

Blood alcohol concentration can be determined directly by gas chromatography (Chapter 1). However, this approach is impractical for testing a driver on the highway. It requires that the suspect be transported to a hospital, where trained medical personnel can take a blood sample, then preserve and analyze it. 

On a truly micro scale (< 10 mg) simple distillation is not practical because of mechanical losses. On a small scale (10-500 mg), distillation is still not a good method for isolating material, again because of mechanical losses but bulb-to-bulb distillations can serve to rid a sample of all low-boiling material and nonvolatile impurities. In research, preparative-scale gas chromatography (Chapters 12, 13) and high-performance liquid chromatography... 

The technique of static headspace gas chromatography (Chapter 5.F.1) proved to be useful in our laboratory for the quantitative analysis of volatile aldehydes in oxidized human LDL. This method was used to distinguish volatile oxidation products of n-6 polyunsaturated fatty acids (pentane and... 

Experimentally, it is best if both the product and starting material can be detected and their concentrations measured at any time during the reaction. Frequently gas chromatography (Chapter 1) or one of the spectroscopic tools (Chapter 2) is found suitable. Thus, for the first-order disappearance of 2-chloro-2-methylpropane (t-butyl chloride [(CH3)3C1]), if the initial concentration that is, at time t = 0, is b, then at some later time, t = t, after the reaction has progressed for a while, the concentration b will have been reduced by formation of the product p to (b - p) so that... 

This chapter is best read in conjunction with Chapter 35, Gas Chromatography and Liquid Chromatography, and any other chapters appropriate to the operation of a mass spectrometer. 

One may also be able to determine the work of adhesion for cases in which the contact angle is zero by using probe liquids, as described later in this chapter. There are also other ways of determining the work of adhesion, such as inverse gas chromatography, which do not depend solely on capillary measurements (surface tension and contact angle). This too will be discussed later. 

This present chapter will not focus on the statistical theory of overlapping peaks and the deconvolution of complex mixtures, as this is treated in more detail in Chapter 1. It is worth remembering, however, that of all the separation techniques, it is gas chromatography which is generally applied to the analysis of the most complex mixtures that are encountered. Individual columns in gas chromatography can, of course, have extremely high individual peak capacities, for example, over 1000 with a 10 theoretical plates column (3), but even when columns such as these are... 

Chromatography is a separation process employed for the separation of mixtures of substances. It is widely used for the identification of the components of mixtures, but as explained in Chapters 8 and 9, it is often possible to use the procedure to make quantitative determinations, particularly when using Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC). 

Maximum benefit from Gas Chromatography and Mass Spectrometry will be obtained if the user is aware of the information contained in the book. That is, Part I should be read to gain a practical understanding of GC/MS technology. In Part II, the reader will discover the nature of the material contained in each chapter. GC conditions for separating specific compounds are found under the appropriate chapter headings. The compounds for each GC separation are listed in order of elution, but more important, conditions that are likely to separate similar compound types are shown. Part II also contains information on derivatization, as well as on mass spectral interpretation for derivatized and underivatized compounds. Part III, combined with information from a library search, provides a list of ion masses and neutral losses for interpreting unknown compounds. The appendices in Part IV contain a wealth of information of value to the practice of GC and MS. 

Gas chromatography/mass spectrometry (GC/MS) is the synergistic combination of two powerful analytic techniques. The gas chromatograph separates the components of a mixture in time, and the mass spectrometer provides information that aids in the structural identification of each component. The gas chromatograph, the mass spectrometer, and the interface linking these two instruments are described in this chapter. 

The combination of chromatography and mass spectrometry (MS) is a subject that has attracted much interest over the last forty years or so. The combination of gas chromatography (GC) with mass spectrometry (GC-MS) was first reported in 1958 and made available commercially in 1967. Since then, it has become increasingly utilized and is probably the most widely used hyphenated or tandem technique, as such combinations are often known. The acceptance of GC-MS as a routine technique has in no small part been due to the fact that interfaces have been available for both packed and capillary columns which allow the vast majority of compounds amenable to separation by gas chromatography to be transferred efficiently to the mass spectrometer. Compounds amenable to analysis by GC need to be both volatile, at the temperatures used to achieve separation, and thermally stable, i.e. the same requirements needed to produce mass spectra from an analyte using either electron (El) or chemical ionization (Cl) (see Chapter 3). In simple terms, therefore, virtually all compounds that pass through a GC column can be ionized and the full analytical capabilities of the mass spectrometer utilized. 

Detection in SFC can be achieved in the condensed phase using optical detectors similar to those used in liquid chromatography or in the gas phase using detectors similar to those used in gas chromatography. Spectroscopic detectors, such as mass spectrometry and Fourier transform infrared spectroscopy, are relatively easily interfaced to SFC compared to the problems observed with liquid mobile phases (see Chapter 9). The range of available detectors for SFC is considered one of its strengths. 

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