The Influence of Mobile Phase Acidity and Counterion Type and Concentration on the Retention Behaviour of Urinary Catecholamines and Sample Impurities in Ion-Pair Reversed-Phase Liquid Chromatography

Abstract

Octyl silica reversed-phase material was used as a support for dynamically coated anion surfactant, octyl sulphate, acting as an ion-pairing agent for retention of biogenic amines. In this system the influence of counterion type and concentration on retention behaviour of the analytes was studied. The strongest competitive effect of all counterions studied /Li, Na, K, NH/ exerted potassium and ammonium. However, the effect⁴ of potassium was lower than expected according to known value of relative selectivity. The accompanying anion and pH in range of 3,6 to 5,5 did not influence the retention noticeable. Regarding determination of catecholamines in urine after a rapid alumina cleanup, a simple ammonium acetate mobile phase of pH 5,4 gave best results with respect to separation of amines from interfering substances present in the sample.