Dependence of HETP upon resin particle size and solution flow-rate in high-speed ion-exchange chromatography

Abstract

In order to obtain a method for selecting the optimum experimental conditions for achieving difficult separations in high-speed ion-exchange chromatography, the dependence of the height equivalent to a theoretical plate (HETP) on the solution flow-rate and resin particle size was studied. The HETP has been measured for the nickel—zinc ion exchange (permutation front) at different flow-rates and for severla fractions of variable sizes obtained by elutriation from the same variety of a commercially available cationic resin, Dowex 50W-X8 (−400 mesh). For a given particle diameter, d p , the HETP ( H) was found to vary with the solution flow-rate, u, according to the equation ▪ where α depends on the particle size: it decrease as d p increases, e.g., from 0.9 to 0.4 when d p varies from 20 to 100 μm, tending to a limiting value which was found to be dependent on the exchange reaction studied. On the other hand, at a constant flow-rate, H was found to vary with d p according to the equation ▪ where β depends on the solution flow-rate: it decreases slowly as u increases. The influence of these parameters on the column efficiency, and of the pressure drop that results from using high flow-rates and very small particles, are discussed.