Potentiometric Titration of Triazolethiols and Tetrazolethiols with Iodine in Alkaline Medium

Abstract

The iodimetric determination of triazolethiols and tetrazolethiols in alkaline medium is presented. The volumetric titration with potentiometric end-point detection was applied. The range of determination, in which the error is lower than 1%, is 20-2 000 μmol for 1H-1,2,4-triazole-3-thiol (1), 25-1 000 μmol for 3-phenyl-1H-1,2,4-triazole-5-thiol (2), 25-500 μmol for 4-methyl-5-(trifluoromethyl)-4H-1,2,4-triazole-3-thiol (3), 50-500 μmol for 3-amino-1H-1,2,4-triazole-5-thiol (4), 10-1 000 μmol for sodium (5-mercapto-1H-tetrazol-1-yl)acetate (5), 125-500 μmol for 1-phenyl-1H-tetrazole-5-thiol (6) and 50-1 000 μmol for 1-(4-hydroxyphenyl)-1H-tetrazole-5-thiol (7). The relative standard deviation for all determinations was below 1%. The shape of potentiometric titration curve of 6 and 7 is noteworthy at higher concentrations of sodium hydroxide and depends on the type of the indicator electrode (platinum, gold). An introduction of iodine results in a strong potential drop. Some systems do not follow the Nernst equation.