HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF AMINO-ACIDS, PEPTIDES AND PROTEINS .129. CERAMIC-BASED PARTICLES AS CHEMICALLY STABLE CHROMATOGRAPHIC SUPPORTS

Porous zirconia based particles have been modified using different der ivatisation procedures. The modified particles were characterised in t erms of their accessible surface areas and degree of surface coverage of the bounded or physicoated phases utilising the strong and specific adsorption of phosphate ions to the zirconia surface. The hydroxyl gr oup density was determined by a H-1 NMR technique. The particles were modified by immobilising different silanes to introduce either hydroph obic ligands or reactive groups onto the zirconia surface. In the latt er case, various ligands were then covalently attached to the activate d supports. Using this type of modification, n-octadecyl- (C18), carbo hydrate- and Cibacron Blue F3GA-modified zirconia particles were produ ced. Furthermore, polymeric coated particles were prepared either by u sing polybutadiene or by cross-linking the carbohydrate modified sorbe nts. The pH stability of the different sorbents were determined in bat ch experiments and under chromatographic conditions. The leakage of li gands was monitored by UV absorption and by employing radioactively la belled ligands. The performance of the C18 reversed-phase modified zir conia in packed columns was also used as an indicator of changes in th e surface chemistry following pH stability tests. The experimental res ults indicate that the Cibacron Blue F3GA dye-modified sorbent was sta ble up to pH 10.5, the C18 reversed-phase packing up to pH 13 and the carbohydrate-bonded phase up to pH 12. These investigations substantia te the favourable chemical and physical characteristics anticipated fo r surface modified zirconias for potential use as chromatographic adso rbents.