An electrochemical study of tinidazole at mercury electrodes

Abstract The electrochemical behaviour of 1-[2-(ethylsulphonyl)ethyl]-2-methyl-5-nitro-1 H -imidazole (tinidazole) was studied by normal pulse and reverse pulse polarography. In aqueous solutions of pH 2.5–4.8 containing no surfactant, tinidazole gives rise to two irreversible cathodic waves, one (I) corresponding to a four-electron electrode reaction and the other (II) to a two-electron reaction; at higher pH the limiting current of I increases at the expense of II until only a single wave for a six-electron reaction is observed at pH > 7.5. A mechanism for the reaction of wave I under the various experimental conditions is suggested. In strongly alkaline media tinidazole decomposes; the kinetics of this process were studied by normal pulse polarography and the second-order rate constant is reported. In basic solutions containing dimethyl formamide or sodium lauryl sulphate, wave I splits into two or three waves; when the splitting is complete, the electrode reaction corresponding to the first wave I′, is the reversible formation of the anion radical, and the formal potential of the tinidazole/anion radical system can be determined.