Chemical methods in gas chromatography,

V.G. Berezkin, Chemical Methods in Gas Chromatography, Elsevier, Amsterdam (1981). 

N. A. Parris, Instrumental Liquid Chromatography, a Practical Manual on High-Performance Liquid Chromatographic Methods (Journal of Chromatography Library, Vol. 27), Elsevier, Amsterdam, 2nd revised ed., 1984 J. Drozd, Chemical Derivatization in Gas Chromatography (Journal of Chromatography Library, Vol. 19), Elsevier, Amsterdam, 1981 J. F. Lawrence and... 

Interest in this method has decreased since advances made in gas chromatography using high-resolution capillary columns (see article 3.3.3.) now enable complete identification by individual chemical component with equipment less expensive than mass spectrometry. 

Analytical separations may be classified in three ways by the physical state of the mobile phase and stationary phase by the method of contact between the mobile phase and stationary phase or by the chemical or physical mechanism responsible for separating the sample s constituents. The mobile phase is usually a liquid or a gas, and the stationary phase, when present, is a solid or a liquid film coated on a solid surface. Chromatographic techniques are often named by listing the type of mobile phase, followed by the type of stationary phase. Thus, in gas-liquid chromatography the mobile phase is a gas and the stationary phase is a liquid. If only one phase is indicated, as in gas chromatography, it is assumed to be the mobile phase. 

EPA. 1986j. Method 8000. Gas chromatography. In Test methods for evaluating solid waste. Vol IB, Laboratory manual, Physical/chemical methods. SW846. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington DC, 3rd ed. 

This chapter describes basic physico-chemical relations between the gas phase transport of atoms and molecules and their thermochemical properties, which are related to the adsorption-desorption equilibrium. These methods can either be used to predict the behavior of the adsorbates in the chromatographic processes, in order to design experiments, or to characterize the absorbate from its experimentally observed behavior in a process. While Part I of this chapter is devoted to basic principles of the process, the derivation of thermochemical data is discussed in Part n. Symbols used in the following sections of Part I are described in Section 5. For results, which were obtained applying the described evaluation methods in gas-adsorption chromatography, see Chapters 4 and 7 of this book. 

Shcherbakova, Petrova, and co-workers (258-263) studied the chemical modification of silica for applications in gas chromatography (for example, in the adsorption separation of hydrocarbons by gas chromatographic methods). The adsorption properties are investigated as a function of the degree of surface modification with ClSi(CH3)3. A number of silica samples were chemically modified so that they would have the desired adsorption properties (17). Chemical modification is an effective means of changing the shape of adsorption isotherms. 

The subtraction method is widely used in gas chromatography (GC) for the qualitative and quantitative analysis of complex mixtures. It is a modification of the method of selective separation and is based on selective removal of one or a group of components from the test mixture. Removal (subtraction) may be achieved either by a chemical reaction leading to the formation of involatile (or, on the contrary, super-volatile, according to the experimental conditions) compounds from a number of components of the mixture being analysed, or by physical methods leading to the formation of a new involatile (e.g., adsorption) phase for a number of components. 

Martin et al. [24] were the first to apply chemical amplification reactions in gas chromatography. They used Emich s system of reactions to increase the amount of carbon dioxide. The amplification system consisted of three stages, each involving a series arrangement including an oven for reduction of carbon dioxide with charcoal and an oven for oxidation of carbon monoxide to carbon dioxide with copper oxide. The experimental gain factor found for this system was 7,45 (theoretical value 8.0). Martin et al. [24] pointed out the promising nature of this method for GC. 

U.S. Environmental Protection Agency (EPA), Method 8410, Gas chromatography/fourier transform infrared (GC/FT-IR) spectrometry for semivolatile organics capillary column. Revision 0, In Online Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (SW-846), Office of Solid Waste, 1994, http //www.epa.gov/epaoswer/hazwaste/test/pdfs/8410. 

HS is generally recalcitrant to any analytical approach, and its chemical structure can only be analyzed after it is broken into low molecular weight compounds by some kinds of degradation. Among the various methods, pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) is currently most commonly used, in which HS is thermally degraded by pyrolysis, the pyrolysate is separated by a gas chromatogram column, and identihed by mass spectrometry. 

BIOLOGICAL PROPERTIES Koc 5,181 leaching is only expected to be quick in sandy soils % degraded under anaerobic continuous flow conditions 4% in air, half of it may be broken down to other chemicals within 60 days in water, half of it may be broken down tc other chemicals within 30 days readily breaks down in soil considerable dispersion is expected did not biodegrade in an anaerobic culture incubated for 48 hrs 37°C under anaerobic conditions with domestic wastewater as the innoculum, 100% was removed after 7 days incubation 25°C soil, surface water, and aerobic half-lives 4 weeks-6 months ground water half-life 8 weeks-12 months anaerobic half-life 16 weeks-24 months can be detected in water by EPA method 612 methylene chloride extraction followed by concentration, gas chromatography plus electron capture detection, or EPA Method 625 gas chromatography plus mass spectrometry... 

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