How to generate peak capacity in column liquid chromatography: The Halász nomograms revised

Abstract

For the separation of complex samples it is necessary to run the analyses on a chromatographic set-up with high peak capacity. The concept of peak capacity is broader than the one of the theoretical plate numbers because it covers both the column characteristics and the run time of the separation. Therefore, a desired peak capacity can be obtained with many combinations of particle diameter, column length, pressure, and analysis time: either with a short column, small-diameter packing, short analysis time, and high pressure; or with less pressure at the expense of a longer column, larger-diameter packing, and longer analysis time. These combinations can be presented in the form of nomograms with the analysis time as x-axis and the peak capacity as y-axis and including particle diameter, column length, and pressure as parameters. The practical limits of the peak capacity are given by the maximum pressure delivered by the pump in use. These considerations are valid for isocratic and gradient separations as well. They are based on a 1982 paper by Halász and Görlitz and apply the concept of HPLC columns used at their Van Deemter optimum.