Liquid chromatography column design

Abstract

A liquid chromatography column design protocol is described utilizing three data bases which are defined as performance criteria, instrument constraints and elective variables. The optimum column length, column radius and particle size of the packing to provide minimum analyses time can be calculated from the information contained in these three data bases. An explicit equation is also derived to permit the optimum particle diameter to be calculated. It is shown that if the inlet pressure is limited, small particles are only suitable for use in short columns for simple separations. Conversely, difficult separations can only be achieved with larger particles packed in long columns. In liquid chromatographic analyses, operating at 6000 p.s.i. as opposed to 4000 p.s.i. results in a proportional reduction in analysis time (about 30%). It follows that a maximum inlet pressure of 4000 p.s.i. appears to be quite adequate and is to be recommended for general liquid chromatographic analysis. The optimum k′ value of the first solute of the critical pair of a complex mixture can range between 2 and 6; furthermore the optimization procedure compensates for changes in diffusivity by corresponding changes in optimum particle diameter and optimum column length. Consequently the numerical value of solute diffusivity is not critical. The quality of the packing remains important even for fully optimized columns and consequently, the best packing procedures should always be employed.