Influence of the particle size distribution of the packing material in reversed-phase high-performance liquid chromatography

Abstract

The influence of a large particle size distribution of reversed-phase silica gel packing materials in high-performance liquid chromatography (HPLC) was studied. Mixtures were prepared with ROSiL-C 18-D materials with mean particle sizes of 3, 4, 5, 6, 8 and 10 μm. The efficiency of columns packed with mixtures of different compositions was measured and the usual chromatographic parameters were deduced. The conclusion is that a large particle size distribution has no influence on column efficiency if the eluting speed is kept around the optimum value. At higher solvent flow-rates there is a small negative effect. At all eluting speeds a larger particle size distribution has a negative effect on back-pressure and on separation impedance. A good practical ratio for the diameters of larger over smaller particles in a chromatographic material is about 1.5 to 2 for the ratio d p 90/ d p 10. The negative effect of fines or dust in column packing materials is stressed.