DETERMINATION OF SOLUTE RETENTION FACTORS IN RPLC WITH PURE WATER AS EFFLUENT USING A NUMERICAL METHOD BASED ON THE OŚCIK'S EQUATION

Abstract

A numerical method based on the linear form of the Ościk equation was used for calculation of the logarithms of the retention factors of alkylbenzenes, PAHs, and several polar monosubstituted benzenes of a RPLC system with pure water as mobile phase. The author used a system consisting of a column packed with LiChrospher RP-18e and mobile phases containing methanol and acetonitrile as organic modifier of the mobile phase. Also, the influence of the kind of the organic modifier of the mobile phase as well as the range of its concentration on the calculated log kw values was studied. Moreover, the correlations between the log kw values determined by various methods and the partition coefficients in the n-octanol/water system (log P) have been presented. The log kw values calculated by the numerical method do not practically depend on the concentration range of the organic modifier and show the best linear correlations with the experimental log P values, number of carbon atoms in alkylbenzenes (nC), and the log kw values determined by linear extrapolation from log k dependence on the volumetric fraction of methanol.