Enantioselective assay for the determination of nisoldipine in dog, rat and mouse plasma by chiral microbore high-performance liquid chromatography combined with gas chromatography-mass spectrometry

Abstract

A sensitive, selective and validated method for the enantioselective determination of (+)- and (−)-nisoldipine in rat, mouse and dog plasma following administration of nisoldipine racemate is described. The alkalized plasma samples containing [ 13C 4]nisoldipine racemate as internal standard (ISTD) were extracted once with toluene. The enantiomers of nisoldipine were quantitatively separated by high-performance liquid chromatography on a 250 × 2 mm I. D. column containing tris(4-methylben-zoate)-modified cellulose on silica. The fractions containing either the (+) or (−)-enantiomer of the analyte and [ 13C 4]ISTD were analysed by gas chromatography with mass-selective detection in the single-ion monitoring mode. The limits of determination and detection were 0.5 and 0.2 ng/ml, respectively, the total precision was better than 7% (R.S.D. at 5 and 50 ng/ml, n = 35) and the accuracy was better than 10% (0.5–100 ng/ml, n = 23). The sum of the concentrations of the enantiomers determined with this assay corresponds to the concentration of the racemate determined independently by capillary gas chromatography with electron-capture detection (accuracy better than 15%, 1–80 ng/ml). The method was used for the analysis of more than 500 plasma samples obtained from toxicokinetic studies.