Capillary gas chromatographic determination with nitrogen-phosphorus detection of the calcium antagonist nicardipine and its pyridine metabolite M-5 in plasma.

A capillary gas chromatographic method with nitrogen-phosphorus detection for the simultaneous determination of nicardipine and its pyridine metabolite M-5 was developed. The method involves extraction of the plasma with hexane-methylene chloride (1:1, v/v), followed by evaporation of the organic phase. The extract is injected into a fused-silica capillary column coated with cross-linked 5% phenyl-methylsilicone. A temperature gradient (85-285 degrees C) is applied and the two products and the internal standard can be separated within 22 min. The limit of detection is 0.5 ng/ml for both products. The method is suitable for pharmacokinetic studies in humans.