Simultaneous determination of nitrendipine and one of its metabolites in plasma samples by gas chromatography with electron-capture detection

A sensitive method for GC-ECD simultaneous determination of nitrendipine and its pyridine metabolite M1 in human plasma is described. Felodipine was used as the internal standard. The plasma samples were extracted with toluene. One microlitre of the extract was injected onto the capillary column (polymethylsiloxane) and measured with electron-capture detector. The developed method showed to be linear over the range 0.25-70 for nitrendipine and 0.3-61 ng/ml for its metabolite M1 with an inter-day and intra-day precision in terms of R.S.D. lower than 8% except the concentrations near lowest limit of quantification (LLOQ) (<11% R.S.D.). The LLOQ for nitrendipine was 0.25 and 0.3 ng/ml for its metabolite, respectively. The analytical recovery was 94% for nitrendipine and 89% for its pyridine metabolite M1. This GC-ECD method was developed for being used in clinical pharmacokinetic studies.