Polarographic studies of some organic compounds

Abstract

Polarographic behaviors of vanillin and isovanillin have been investigated. Each of these substances showed a clear reducing wave by using 0.25 M NH4Cl as a supporting electrolyte, 0.04 M Britton-Robinson buffer in 80% alcoholic solution containing 0.028% gelatin. The polarographic determination of each of the substances was possible since their wave heights were proportional to the concentration in the pH range of 3.28.1 and concentration range of 0.11.0 mM. With an increase in pH value, the half-wave potentials of both of these substances were shifted to the negative side at below pH 6.6 and to the positive side at above pH 6.6. The diffusion coefficient calculated from the Stokes-Einstein equation was applied to the Ilkovic equation to determine the electron number, from which was confirmed the mechanism of reduction at the dropping mercury electrode.Polarographic behaviors of phenylmercuric acetate have been investigated. This substance showed a clear two-step wave in a 80% alcoholic solution containing 0.028% gelatin, 0.25 M NH4Cl as a supporting electrolyte, and 0.04 M Britton-Robinson buffer. The first half-wave potential of the first step wave showed only a slight change with change in pH and concentration, but the half-wave potential of the second step wave was shifted toward the negative side by changes in pH and concentration. Since the wave heights were proportional to the concentration with the exception of the second step wave at pH 3.3, quantitative determination was possible within the concentration range of 0.052.00 mM. However, the reproducibility of wave heights in acid reaction was slightly irregular, so the determination should be made at pH 8 or at around neutral reaction. Quantitative determination was possible up to 2.5 mM and pH 8. The diffusion coefficient calculated from the Stokes-Einstein equation was applied to the Ilkovic equation to determine the electron number, from which was confirmed the mechanism of reduction at the dropping mercury electrode; and the result agreed with the report of Benesch.