Potentiometric enantioselective membrane electrode for s-enalapril assay

Abstract

A novel potentiometric, enantioselective membrane electrode based on graphite paste (graphite powder and paraffin oil), impregnated with 10-3 mol/L 2-hydroxy-3-trimethylammoniopropyl-β-cyclodextrin (as chloride salt) solution, has been constructed. The potentiometric, enantioselective membrane electrode can be used for the reliable assay of S-enalapril as raw material and from its pharmaceutical formulations in the concentration range of 3.6 x 10-5 - 6.4 x 10-2 mol/L, with a detection limit of 1.0 x 10-5 mol/L and with an average recovery of 99.96% (RSD = 0.098%), using a chronopotentiometric (zero current) technique. The enantioselectivity was determined versus D-proline and it was shown that only L-proline is the main interfering compound. The surface of the electrode can be regenerated by simply polishing to obtain a fresh surface which is ready to be used in a new assay.