High-performance liquid chromatographic determination of verapamil in plasma by fluorescence detection.

A rapid and highly sensitive method is reported for the quantitative determination of verapamil in plasma. Verapamil and its internal standard are extracted from alkalinized plasma with heptane and then back-extracted into dilute sulfuric acid. An aliquot is injected directly into a high-performance liquid chromatograph, separated by reversed-phase chromatography, and quantified by a fluorescence detector. The procedure is suitable for the routine determination of verapamil in plasma in concentrations as low as 1 ng/ml.