Voltammetric determination of weak bases based on oxidation of α-tocopherol in an unbuffered solution

Linear sweep voltammetry of weak bases with alpha-tocopherol was investigated at a plastic formed carbon electrode in methanol. A weak base present in an alpha-tocopherol solution gave rise to a new peak (oxidation prepeak) resulting from the oxidation of alpha-tocopherol at a potential more negative than that of alpha-tocopherol. With an increase in pK(b) of the base, the half-peak potential of the oxidation prepeak was found to shift to a less negative potential. The prepeak height was noted to depend linearly on the concentration of base compound up to a certain value, the same as that for alpha-tocopherol in the electrolyte. The electrode oxidation reaction was shown to occur in accordance with a prepeak current controlled by diffusion of weak base to the electrode surface in unbuffered solution. A new voltammetric determination of such weak bases as aniline, clotrimazole, cimetidine, disopyramide, lidocaine, medazepam, metoclopamide, and N,N-diethylaniline was developed. (C) 2003 Elsevier B.V. All rights reserved.