The measurement of nitrite is based on the electrochemical reduction at gol
d electrode of thionitrite, which is the product of reaction between nitrit
e and 3-mercaptopropanoic (MPA). Visible absorption spectra show that S-N=O
of thionitrite is involved in the electrochemical reduction at the gold el
ectrode. The result of coulometric analysis indicates that the electrochemi
cal reduction is a two-electron transfer process. The dependence of peak po
tential on pH provides evidence that two protons are involved in the electr
ochemical reaction. A mechanism for the reaction is proposed. The effect of
MPA concentration on the current response in the presence of nitrite is al
so discussed. The detection limit is 5 mu mol/l and the peak current is lin
ear with the concentration of nitrite over the 5x10(-6)-5x10(-3) mol/l rang
e. This method is used for the determination of nitrite in pickled vegetabl
e water and the results are satisfactory. (C) 1999 Elsevier Science B.V. Al
l rights reserved.