CARBON ADSORBENTS IN GAS-ADSORPTION CHROMATOGRAPHY

The possibilities for the use of graphitized thermal carbon black (GTCB), especially in the separation of stereoisomers by gas chromatography, are surveyed. It is shown that the retention on GTCB, a monoatomic, highly homogeneous adsorbent, is defined mainly by the geometry of molecules. In spite of its great advantages, GTCB has two drawbacks: the carbon particles are not mechanically strong enough, and it has a very high adsorption potential, which leads to higher temperatures of separation in comparison with liquid stationary phases. These disadvantages can be removed by chemical and adsorption modifications. The influence of such modifications on adsorption and chromatographic properties has been systematically studied for carbon black and carbochrome. In the case of adsorption modification, high-molecular-mass organic substances with various functional groups, and also polymers with flexible and rigid polymer links, were used as modifying agents. Of great interest are modifying agents with a flat structure of the molecules, such as phthalocyanines, etioporphyrins, crown ethers and their metallic complexes. The use of chemical and adsorption modifications allows one to change the chemistry of the surface in a very wide range and to obtain selective adsorbents. © 1990.