Polarographic determination of methionine by measurement of the nickel(II) catalytic pre-wave

Abstract

Methionine yields a nickel(II) catalytic polarographic pre-wave in borate media. This pre-wave was studied as a function of the composition and pH of the borate medium, the nickel(II) concentration, the addition of neutral salts and the methionine concentration. The best system for determining methionine is: 2 × 10^–4M nickel(II)-0.06 M disodium tetraborate-nitric acid (pH 8.6). D.c. polarography is suitable for the determination of methionine over the concentration range 1 × 10^–5–8 × 10^–5M. In differential-pulse polarography the calibration graph is linear over the methionine concentration range 3 × 10^–6–55 × 10^–6M.