HORIZONTAL POLYMERIZATION OF MIXED TRIFUNCTIONAL SILANES ON SILICA .2. APPLICATION TO CHROMATOGRAPHIC SILICA-GEL

A now surface bonding scheme for monolayers on silica recently reported1,2 was designed to combine the superior hydrolytic stability of self-assembled monolayers with the selectivity and reproducibility of monomeric stationary phases. In this work, the scheme is shown to work very effectively for chromatographic silica gel. A mixture of CH3(CH2)17SlCl3 and CH3(CH2)2SlCl3 is horizontally polymerized onto 40- and 50-mum-diameter porous silica gel particles. C-13 NMR and microanalysis are used to establish that a coverage consistent with horizontal polymerization is achieved. The chromatographic retention behavior of a set of test solutes is shown to be similar to that for conventional monomeric C18 phases. The repeated synthesis of the new phase is shown to give reproducible retention times for benzo[a]pyrene and aniline. The hydrolytic stability is demonstrated to be greatly improved over that of a monomeric C18 stationary phase: the new phase is stable to at least 2400 column volumes of pH 1.8 solution and stable to at least 900 column volumes of pH 10.0 solution.