Gas and liquid chromatography

The quality control analyses of these chemicals are performed using almost the whole range of trace analysis techniques available. Among the most important are atomic absorption spectrophotometry in all its forms, ICP emission spectrometry, and ICP mass spectroscopy, ion chromatography, gas and liquid chromatography, ultraviolet and visible absorption spectrophotometry, voltammetry, and spectro-fluorimetry. 

The effect of three independent spreading mechanisms on efficiency in column chromatography (gas and liquid) is expressed by the Van Deemter equation, the classical form of which is... 

Smith, R.M., Gas and Liquid Chromatography in Analytical Chemistry, Wiley, Chichester, U.K., 1988. Smith, R.M. and Busch, K.L., Understanding Mass Spectra A Basic Approach, Wiley, Chichester, U.K., 1998. Snyder, A.R, Biochemical and Biotechnological Applications of Electrospray Ionization Mass Spectrometry, Oxford University Press, Oxford, 1998. 

R. L. Grob and M. A. Kaiser, Environmental Problem Solving Using Gas and Liquid Chromatography, Elsevier, Amsterdam, The Netherlands, 1982. 

Carnahan, Jr., C. (1993) Gas and liquid chromatography, in Concise Encyclopedia of Materials Characterisation, eds. Cahn, R.W. and Lifshin, E. (Pergamon Press, Oxford) p. 169. 

There are a number of causes of peak asymmetry in both gas and liquid chromatography, including heat of adsorption, high activity sites on the support or absorbent, and nonlinear adsorption isotherms. Assuming that good quality supports and adsorbents are used, and the column is well thermostatted, the major factor causing peak asymmetry appears to result from nonlinear adsorption isotherms. 

Various types of derivatisation have now been developed for both gas and liquid chromatography. For more detailed information regarding the choice of a suitable derivative for a particular analytical problem, the appropriate works of reference should be consulted.62,63... 

In gas-liquid partition chromatography (GLPC), the stationary phase is a liquid that coats the particles in the tube or the walls of the tube. Often the tube itself is very narrow and long, perhaps 100 m, and has to be coiled (Fig. 4). Solutes are separated, as in liquid chromatography, by their relative solubility in the gas and liquid phases. In... 

Using a simple solvent extraction procedure to minimize matrix effects, a diclofop-methyl immunoassay was developed for milk, a number of edible plant products, and other matrices. Gas chromatography (GC) and liquid scintillation counting (LSC) of a C-labeled analyte were used as reference methods to compare with enzyme immunoassay (EIA) results. The methods were well correlated, with comparison of EIA... 

During their passage through the column, sample molecules spend part of the time in the mobile phase and part in the stationary phase. All molecules spend the same amount of time in the mobile phase. This time is called the column dead tine or holdup time (t.) and is equivalent to the tine required for an unretained solute to reach the detector frsolute retention time (t,) is the time between the instant of saiq>le introduction and when the detector senses the maximum of the retained peak. This value is greater than the column holdup time by the amount of time the solute spends in the stationary phase and is called the adjusted retention time (t, ). These values lead to the fundamental relationship, equation (1.1), describing retention in gas and liquid chromatography. 

A form of flux calcined silica of low surface area used mainly as a filter aid and inert support in gas and liquid-liquid chromatography. 

Retention in SFC is a complex function of the experimental parameters and is not as easily rationalized as in the case of gas and liquid chromatography. Retention in SFC is dependent upon temperature, pressure, density, sample concentration, composition of the mobile phase and the composition of the stationary phase. Many of these variables are interactive nd do not change in a... 

A schematic diagram of a chromatograph for SFC is shown in Figure 6.10. In general, the instrument components are a hybrid of components developed for gas and liquid chromatography that have been subsequently modified for use with supercritical fluids. Thus, the. fluid delivery system is a pump modified for pressure control and the injection system a rotary valve similar to components used in liquid chromatography. The column oven and... 

The rapid and reversible formation of complexes between some metal ions and organic compounds that can function as electron donors can be used to adjust retention and selectivity in gas and liquid chromatography. Such coordinative interactions are very sensitive to subtle differences in the composition or stereochemistry of the donor ligand, owing to the sensitivity of the chemical bond towards electronic, steric and strain effects. A number of difficult to separate mixtures of stereoisomers and isotopomers have been separated by complexation chromatography. 

Capillary electrophoretic separations are performed in small diameter tubes, made of Teflon, polyethylene, and other materials. The most frequently used material is fused silica. Fused silica capillaries are relatively inexpensive and are available in different internal and external diameters. An important advantage of a fused silica capillary is that the inner surface can be modified easily by either chemical or physical means. The chemistry of the silica surface is well established due to the popularity of silica surfaces in gas chromatography (GC) and liquid chromatography (LC). In capillary electrophoresis, the silica surface is responsible for the EOF. Using surface modification techniques, the zeta potential and correspondingly the EOF can be varied or eliminated. Column fabrication has been done on microchips.13... 

Gas and liquid chromatography directly coupled with atomic spectrometry have been reviewed [178,179], as well as the determination of trace elements by chromatographic methods employing atomic plasma emission spectrometric detection [180]. Sutton et al. [181] have reviewed the use and applications of ICP-MS as a chromatographic and capillary electrophoretic detector, whereas Niessen [182] has briefly reviewed the applications of mass spectrometry to hyphenated techniques. 

Hawk, G.L. and Little, J.N., Derivatization in Gas and Liquid Chromatography in Zymark Sample Preparation Program (SPF CT 1 103), Zymark Corporation, Hopkinton, MA, 1982. 

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