METHODS OF EQUILIBRIUM CONCENTRATION FOR THE GAS-CHROMATOGRAPHIC DETERMINATION OF TRACE VOLATILES

This review deals with a gas chromatographic technique based on the use of equilibria in the condensed phase-gas system, which is currently in the stage of intense development. Problems bearing on the usefulness of different variants of headspace analysis and of related methods in reducing the threshold of the gas chromatographic determination of volatile impurities in objects taken in any aggregate state are considered. When analysing impurities in solid and liquid objects, major attention is focused on the specific features of headspace analysis and methods of improving its sensitivity. For gas objects the same problems are treated in the context of the reverse technique, i.e., equilibrium saturation of a condensed phase with the gas to be analysed. The theory and practice of equilibrium concentration, including headspace analysis techniques, are developing so fast that even fairly recent reviews and monographs no longer reflect the state of the art of this area in organic analysis. The methods of headspace analysis and its new modifications provide fairly accurate and selective determinations of a variety of impurities present in complex mixtures at the mu-g/l level or lower, and find broad application in the analysis of environmental samples and in biology, medicine, geochemistry, oceanology, power engineering, etc. The review covers studies made in the field of headspace concentration and related methods in the last 10-12 years. Attention is focused primarily on the description of the fundamentals of these methods and the areas of their applicability.