Abstract
The measurement of nitrite is based on the electrochemical reduction at gold electrode of thionitrite, which is the product of reaction between nitrite and 3-mercaptopropanoic (MPA). Visible absorption spectra show that –S–NO of thionitrite is involved in the electrochemical reduction at the gold electrode. The result of coulometric analysis indicates that the electrochemical reduction is a two-electron transfer process. The dependence of peak potential on pH provides evidence that two protons are involved in the electrochemical reaction. A mechanism for the reaction is proposed. The effect of MPA concentration on the current response in the presence of nitrite is also discussed. The detection limit is 5 μmol/l and the peak current is linear with the concentration of nitrite over the 5×10 −6–5×10 −3 mol/l range. This method is used for the determination of nitrite in pickled vegetable water and the results are satisfactory.
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