Determination of calcium dobesilate in human plasma using ion-pairing extraction and high-performance liquid chromatography

A rapid, simple reversed-phase high-performance liquid chromatographic meth od with ultraviolet absorbance detection has been developed for the determi nation of calcium dobesilate in human plasma. Sample processing is based on an ion-pairing extraction with tetra-n-butylammonium hydroxide as cationic pairing ion and dichloromethane. Separation of the investigated calcium do besilate and 2,4-dihydroxybenzoic acid as internal standard was achieved on a Discovery RP-Amide C-16 analytical column with 50 mM, pH 2.5, potassium dihydrogenphosphate buffer-acetonitrile (75:25, v/v) mobile phase. The wave length was set at 305 nm. The limit of quantitation is 100 ng/ml and the ca libration curve is Linear up to 50 mug/ml. Within-day and between-day preci sion expressed as the relative standard deviation is about 10% and the accu racy of the determination did not deviate from 100% by more than +/-10%. Th e developed method was found to be suitable for application in human bioequ ivalence studies. (C) 2001 Elsevier Science B.V. All rights reserved.