CARBON ADSORBENTS AS MATERIALS FOR CHROMATOGRAPHY II - LIQUID-CHROMATOGRAPHY

General physico-chemical characteristics of carbon adsorbents as colum n packings in high performance liquid chromatography (HPLC) are presen ted. The requirements for carbon adsorbents for HPLC and the methods o f their preparation are described. The following methods are discussed : (1) the Guiochon method consisting of curing weak carbon black agglo merates mechanically through depositing benzene pyrolysis products on them; (2) the Dousek method consisting of the reduction of polytetrafl uorethylene at room temperature and the way in which so-called Jade-ca rbon was obtained (the method similar to that used by Zwier and Burke) ; (3) the Unger method in which catalytic gasification of active carbo n in the atmosphere of H-2 + H2O in the presence of ferrurn salt is us ed; (4) the Knox and Berek methods in which phenol-formaldehyde polyme r (Knox) or other organic substances (Berek) are put on the mineral ma trix (silica-Knox) and then are carbonized and the mineral matrix is r emoved from the complex adsorbent; (5) the Nagaoka method in which sph erical carbon globules are obtained by graphitization of spherical cel lulose molecules. All adsorbents prepared in this way can be modified using the methods known for active carbons to obtain a given structure and morphology of carbon deposit. The methods described above allow o ne to obtain adsorbents of optimal parameters for the chromatographic separation. The rules of retention and requirements for the above ment ioned carbon deposits in HPLC are discussed. Besides the carbon adsorb ents the properties and application of Carbopacks and carbon-silica ad sorbents (Carbosils) in HPLC are presented. The role of mono-and multi component solvents in adsorption liquid chromatography and the influen ce of eluent on retention and selectivity of separation of analyzed su bstances are discussed. The attention has been paid to the possibility of applying carbon adsorbents in supercritical chromatography and the possibility of applying numerous carbon adsorbents in HPLC separation s, (C) 1998 Elsevier Science S.A. All rights reserved.