Assay of diltiazem and deacetyldiltiazem by capillary gas chromatography

A highly sensitive gas chromatographic method for the analysis of diltiazem and deacetyldiltiazem in plasma or serum is reported. After silylation with bis (trimethylsilyl) trifluoroacetamide, separation was obtained on a cross-linked fused-silica column and detection was by electron-capture. The minimum measurable concentrations were 3 and 1 ng/ml for diltiazem and deacetyldiltiazem, respectively. Intra- and inter-day coefficients of variation were less or equal to 6.0 and 8.0%, respectively, for both compounds. The method was used to study the kinetics of a single oral dose of 60 mg of diltiazem hydrochloride in a patient with renal failure.