[Preparation of restricted-access media--alkyl-diol silica (ADS) by an improved method]

Alkyl-diol silica (ADS) is a kind of restricted-access media, which can be used for direct injection and analysis of complex biological samples containing bio-macromolecules. A new economical procedure has been developed to prepare ADS packing. At first gamma-glycidoxypropyl group was coupled onto the surface of microporous silica gel (Develosil 60-5 mu) to form epoxy-silica. Prepared epoxy-silica can react with stearic acid in organic solvent to prepare C18 ester-bonded reversed-phase packing. The packing was packed into a column and then the solution of pancreatic lipase was pumped into the column to create enzymoloysis reaction. The stearyl groups on the surface of packing can be removed by the enzymolysis to form a hydrophilic surface. At the same time, inner surface of micropore remains hydrophobic nature due to size exclusion effect of micropore to enzyme molecules. Chromatographic evaluations were carried out and the typical ADS behavior was confirmed.