Determination of nifedipine in human plasma by high-performance liquid chromatography with electrochemical detection.

A rapid, accurate and sensitive high-performance liquid chromatographic assay was developed for the determination of nifedipine in human plasma. A toluene extract of an alkalinized plasma sample was chromatographed on a reversed-phase column with electrochemical detection at +0.95 V. The recovery of nifedipine from plasma was about 100%. The detection limit for nifedipine in plasma was 2 ng/ml using 0.5 ml of sample. The assay gave a linear response over the concentration range 5-400 ng/ml in plasma. The coefficients of variation from 9.6 to 191.0 ng/ml varied between 5.2 to 1.0% and the accuracy did not exceed 3.0%. Photodegradation products and metabolites of nifedipine did not interfere in the analysis. This method allowed the behaviour of nifedipine in humans to be studied.