Properties of low-capacity macroporous anion-exchangers and their use with high-pH eluents for the determination of weak acids in urine

Low-capacity anion-exchangers have been synthesized from the macroporous styrene-divinylbenzene co-polymer Hamilton PRP-1. These anion-exchangers have non-polar adsorbent properties for neutral sample molecules. The dependence of the capacity factor for a polar weak-acid metabolite of the drug polythiazide on the type and concentration of electrolyte, the organic solvent concentration, and pH of aqueous eluents has been studied to characterize the exchangers. As an application, a method has been developed to determine the metabolite in urine at levels as low as 10 ng ml . The method employs the exchangers in both a precolumn, which is used to preconcentrate and clean-up the metabolite from urine, and an analytical column. Eluents containing 0.001-0.01M sodium hydroxide are used to ionize the weak-acid metabolite.