PREDICTION OF RETENTION IN REVERSED PHASE ION-PAIR CHROMATOGRAPHY USING SODIUM DODECYL-SULFATE AS PAIRING ION

A 3 x 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.