Quantitative determination of chlorpromazine and thioridazine by high-performance thin layer chromatography.

An assay for quantitation of chlorpromazine and thioridazine in patient plasma is developed. The procedure utilizes high-performance thin layer chromatography for separation and in situ absorption densitometry for quantitation. Depending upon the HPTLC plate size, 30 to 60 samples may be processed in less than 6 hr, with an intra-assay coefficient of variation of less than 4%. The procedure can be used to measure as little as 10 ng/ml of drug in plasma, well below expected concentrations in patients receiving these medications. Investigations of extraction procedures, sample application procedures, chromatographic conditions, sample derivatization, and in situ absorption densitometry are described.