RETENTION PREDICTION BASED ON THE ELECTROSTATIC MODEL OF REVERSED-PHASE ION-PAIR HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY - EFFECT OF PAIRING ION CONCENTRATION

Based on the electrostatic model of reversed-phase ion-pair chromatography, a practical equation was developed to describe the relationship between the capacity factor of ionic solutes and the eluent concentration of the amphiphilic pairing ion. At constant ionic strength and organic modifier concentration, the logarithm of solute capacity factor can be approximated as a linear function of the logarithm of the pairing ion concentration. The slope of this relationship is determined by the sign and number of charges of the solute ion and the pairing ion. The limitations and the practical use of the proposed model are discussed in detail.