Adjustment of the capacity factor by means of the specific surface area of the adsorbent for optimal separation in liquid-solid chromatography

Abstract

Summary In the optimization of a chromatographic separation with respect to resolution, speed and dilution, the capacity factor is an important parameter. Its influence on the chromatographic characteristics is discussed theoretically. The capacity factor is determined by the distribution coefficient and the phase ratio. Only the phase ratio can be used, however, to adjust the value of the capacity factor without affecting the value of the selectivity coefficient at the same time. Micro-particulate silica and octyl silica with different specific surface areas were investigated experimentally as adsorbents for liquid-solid chromatography. It is shown that the selectivity of these materials is fairly constant for specific surface areas varying over two orders of magnitude. The effect of the adjustment of the specific surface area is demonstrated in the separation of dyestuffs and polynuclear aromatic hydrocarbons by high-pressure liquid chromatography. The application of column switching for optimal separation using two or three columns packed with the same adsorbent but with different specific surface areas is shown.