Utility of small-particle silica in preparative chromatography

Abstract

Three columns filled with octadecylsilane-bonded spherical silica were studied to determine their behavior with different sample loads below and in the “overload” region. The stationary phases were similar as possible, differing only in their particle sizes (8,5 and 3 μm diameter). Optimum and non-optimum flow-rates, as determined by a plot of plate height versus flow-rate, were used with each particle size. Chromatograms were compared using peak width at half-height as a measure of preparative utility, after the method of Perry and Szczerba [ J. Chromatogr., 484 (1989) 267]. It was found that the three particle sizes became equivalent in peak width at a given sample load soon after entering the “overload” region. Although the larger particles gave a slightly wider range of linear peak width to sample load response, at no time did the larger particles offer a greater loading capacity than the smaller particles. Until overloaded, the larger particles gave less sample capacity than the smaller particles. The potential benefits of these findings as they influence throughput are discussed, and the terms “laboratory-scale” preparative high-performance liquid chromatography are defined and discussed in the light of the results.