Prediction of Retention in Reversed Phase Ion-Pair Chromatography Using Sodium Dodecyl Sulphate as Pairing Ion

Abstract

A 3 × 3 factorial design has been applied in the study of the chromatographic behaviour of thirteen protonated amines in reversed phase HPLC using sodium dodecyl sulphate as the pairing ion. The maximum capacity factors (log k'_max ) of the test compounds and the mobile phase pairing ion concentrations that produce the retention maxima (log P_max ), have been correlated to the pK_a , hydrophobicity and connectivity index of the solute, as well as the mobile phase acetonitrile and tetrabutylammonium (TBA) contents. The two dependent variables log K'_max and log P_max , have been shown to be governed mainly by the hydrophobicity of the solutes and, the acetonitrile and mobile phase TBA concentration. The mathematical models generated have been employed to predict experimental conditions for retention optimization of diltiazem and deacetylated diltiazem. The predicted log k'_max and log P_max , have been found to be in agreement with those obtained experimentally.