Development of Novel Inorganic Material for Chromatographic Column Without Particle Packing

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Tetramethoxysilane was hydrolyzed in thepresence of polyethylene oxide having an average molecular weight of 10000 using acetic acid as a catalyst, which gave a wet silica gel with inetrconnected macropores about 2mum wide. The gel was subsequently immersed in aqueous solutions of ammonia with varied concentration for varied periods, then dried by evaporating the solvent, and finally heat-treated at 600ﾟC for 2 hours. The resultant gel retained narrowly distributed mesopores with their median size distributing from 5 to 20nm. The rod-shaped gel thus obtained was clad with a thermoshrinking resin on its side wall, suface-modified by a flow reaction with silane coupling agents, equipped with connecting devices for an ordinary HPLC apparatus, then the separation performance was investigated.A mixture of alkylbenzenes was analyzed using the rod-shaped column with the average macropore diameter of 1.6mum and mesopore diameter of 11nm. The pressure drop for the rod-shaped colummn at the same sample flow rate was less than half that of conventional particle-packed columns. Furthermore, the height equivalent to theoretical plate (HETP) remained almost unchanged for the rod-shaped column between 1mm/s and 5mm/s of linear flow rate, whereas that of conventional particle packed columns increased almost linearly with the flow rate. As a result, the HETP of the rod-shaped column became five times smaller than that of conventional ones. Simmilar difference in the pressure drop and the flowrate dependence of HETP was obsereved also in the case of separation of insulin. These results indicate that the rod-shaped column gives almost an order better separation performance than conventional ones. The superiority of the rod column in the high speed separation was experimentally confirmed to be due to the existence of thin silica skeleton associated with high fraction of macropores.