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

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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 Pmax ), have been correlated to the pKa , 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 Pmax , 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 Pmax , have been found to be in agreement with those obtained experimentally.