Reversed-phase thin-layer chromatography of some angiotensin converting enzyme (ACE) inhibitors and their active metabolites

The chromatographic behaviour of some ACE inhibitors and their active metabolites was examined under conditions of reversed-phase thin-layer chroma- tography on RP-18 silica using water-methanol, water-ethanol and water-acetone as binary solvent systems. The relationship between the RM values and the concen- tration of organic modifier in the mobile phases was linear. It was found that an in- crease in the content of the organic modifier in the employed solvent systems led to a decrease of the RM values, i.e., of the retention. Also, the more hydrophobic com- pounds had a longer retention. Based on regression analysis of the plots, the lipophilicity parameters RM 0 and c0 were calculated. The chromatographically ob- tained lipophilicity parameters were correlated with the calculated log P values.