Coupled-column chromatography on a Chiral-AGP phase for determination of amlodipine enantiomers in human plasma: An HPLC assay with electrochemical detection

A sensitive enantioselective high performance liquid chromatographic assay for determination of the dihydropyridine-type calcium antagonist amlodipine in human plasma samples is described. Chiral chromatography is performed on an alpha(1)-acid glycoprotein column (i.e. Chiral-AGP) and the eluted enantiomers are trapped and compressed on two short columns before final achiral chromatography on a narrow bore column (i.e. Zorbax SB-Ph) using electrochemical detection, Both stereoselective quantitative analysis and enantiomeric ratio analysis, for samples with a known total concentration of amlodipine are described. The quantitative assay shows linearity over the range 0.5-10 ng ml(-1) for the two enantiomers and the limit of detection is about 0.2 ng ml(-1). The method has been applied to a pharmacokinetic study of the enantiomers of amlodipine in human subjects.