Coulometric titration of iodide and iodine with electrolytically generated hypobromite

Abstract Conditions for the quantitative coulometric titration of iodide and iodine with electrolytically generated hypobromite in the presence of borax buffer have been established. Iodide and iodine are oxidized to iodate. The method, with biamperometric indication of the equivalence point, was successfully applied for a wide range of iodide concentrations (6.21–2115μg with reliability intervals of ±0.21–±11μg) and iodine concentrations (24.26–3311μg with reliability intervals of ±0.36–±11.7μg). The determinations are accurate and sensitive even in the presence of large amounts of bromides and chlorides ( Br − I − = 1.2·10 6 and C l − I − =4.0·10 3), as well as in the presence of oxidizing agents such as IO 3 − , BrO 3 − and CrO 4 2− ( I O 3 − /I 2 )=3.2·10 5 , I O 3 − /I 2 =3.1·10 3 , Br O - 3 /I 2 =1.1·10 4 and Cr O 2- 4 /I 2 =1.0·10 4 , as was confirmed by statistical tests. The oxidation mechanism under the conditions of coulometric titrations is discussed.