Rapid Quantification of Valsartan in Human Plasma by Liquid Chromatography using a Monolithic Column and a Fluorescence Detection: Application for Pharmacokinetic Studies

A rapid high-performance liquid chromatographic (HPLC) method using a monolithic column has been developed for determination of valsartan in human plasma. The assay is based on protein precipitation using acetonitrile and fluorescence detection. The assay enables the measurement of valsartan for therapeutic drug monitoring with a minimum quantification limit of 20 ngml^-1. The method involves simple, one-step extraction procedure and analytical recovery was nearly complete. The separation was carried out in reversed-phase conditions using a Chromolith Performance (RP-18e, 100×4.6 mm) column with an isocratic mobile phase consisting of 0.01 M disodium hydrogen phosphate buffer-acetonitrile (60:40 v/v) adjusted to pH 3.5 with diluted phosphoric acid. The excitation and emission wavelengths were set at 230 and 295 nm, respectively. The calibration curve was linear over the concentration range 20-2000 ngml^-1. The coefficients of variation for inter-day and intra-day assay were found to be less than 6%. The assay was applied for the analysis of blood samples from a pharmacokinetic study.