Liquid-chromatographic determination of an angiotensin converting enzyme inhibitor, CGS 13945, and its active metabolite (CGS 13934) in plasma.

An assay for a new orally active angiotensin converting enzyme inhibitor, CGS 13945, and its active metabolite, CGS 13934, in plasma is described. The compounds are extracted from plasma at pH 3 into methylene chloride. The organic layer is evaporated and the reconstituted residue is chromatographed on a reversed-phase column, with ultraviolet detection. The ratios of peak height of both compounds to internal standard are linearly related to their respective concentrations over the concentration range 0.05 to 10 mg/L. As little as 50 ng of drug or metabolite can be measured in 1 mL of plasma. With use of an automated chromatographic system, samples can be analyzed overnight in a continuous unattended run.