Simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method for the quantification of lacidipine in human plasma

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Abstract
A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantification of lacidipine in human plasma using its structural analogue, amlodipine, as internal standard (IS). The method involves a simple single‐step liquid–liquid extraction with tert‐butyl methyl ether. The analyte was chromatographed on an Xterra MS C18 reversed‐phase chromatographic column by isocratic elution with 20 mM ammonium acetate buffer–acetonitrile (10 : 90, v/v; pH 6) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 456.4 → 354.4 and m/z 409.3 → 238.3 were used to measure the analyte and the I.S., respectively. The chromatographic run time was 1.5 min and the weighted (1/x2) calibration curves were linear over the range 0.1–25 ng ml−1. Lacidipine was sensitive to temperature in addition to light. The method was validated in terms of accuracy, precision, absolute recovery, freeze–thaw stability, bench‐top stability and re‐injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 50 and 100 pg ml−1, respectively. The within‐ and between‐batch accuracy and precision were found to be well within acceptable limits (<15%). The analyte was stable after three freeze–thaw cycles (deviation <15%). The average absolute recoveries of lacidipine and amlodipine (IS) from spiked plasma samples were 51.1 ± 1.3 and 50.3 ± 4.9%, respectively. The assay method described here could be applied to study the pharmacokinetics of lacidipine. Copyright © 2004 John Wiley & Sons, Ltd.