Modified Gas‐Solid Chromatography

Abstract

Modified Gas-Solid ChromatographyThe solution of many difficult analytical problems of practical importance and the development of gas-solid chromatography can be achieved, in our opinion, by using modified gas-solid chromatography. Modified gas-solid chromatography is a variant of gas chromatography which uses an adsorbent covered by stable (under the experimental conditions) continuous or island-type layer of organic or inorganic volatile or involatile compounds, whose presence modifies the chemical or structural composition of the adsorbent surface, thus changing the nature and intensity of molecular interactions taking place between different analytes and the surface of the adsorbent. Fig. 5-1 shows the main variants of modified gas-solid chromatography. Of course, hybrid modified chromatography set-ups are some-times also useful (for example, simultaneous operation of both variant II and variant IV).In one of the versions of modified gas-solid chromatography, adsorbents covered by a stable layer of organic or inorganic compounds are used. The presence of modifier changes the chemical composition of the adsorbent surface and therefore the nature and intensity of molecular interactions taking place between the modified surface and the various analytes of a mixture under study. As a result, the adsorption energy of each component of the mixture usually decreases, permitting use of sorbent material at a much lower temperature. The selectivity of the modified stationary phase increases concomitantly. Finally, by changing the nature of the modifying compound and its surface concentration, it is possible to change the absolute and relative retention over a wide range. Capillary Gas Adsorption Chromatography