Direct injection assay of angiotensin-converting enzyme by high-performance liquid chromatography using a shielded...

A rapid and sensitive method for the determination of angiotensin-converting enzyme activity in serum and tissue extracts is described. The procedure is based on the high-performance liquid chromatographic separation of the synthetic substrate hippuryl-L-histidyl-L-leucine from the hydrolysis product hippuric acid. The separation is accomplished by direct injection of biological assay mixtures onto a shielded hydrophobic phase column with isocratic elution.