Specific high performance liquid chromatographic determination of quinidine in serum, blood, and urine.

Summary A reversed-phase high performance liquid chromatographic method for determination of quinidine in serum, blood, and urine has been developed. An alkylnitrile column is used with a mobile phase of acetonitrile in an acetate buffer. The method was rigorously tested and shown to be specific for quinidine using the following methods: (a) comparison of capacity factors among methanolic reference standards of quinidine, known metabolites, and 36 other drugs; (b) comparison of the quinidine capacity factor with the capacity factors from components in patient sera and urines, from which quinidine was selectively removed by thin-layer chromatography; and, (c) correlation of quinidine concentrations in patient sera using ultraviolet absorbance versus fluorescence detection. Application of the method to a single-dose pharmacokinetic study, including serum protein binding and blood/serum concentration ratio measurements, demonstrates excellent sensitivity of the method.