Investigation of polarographic interference between Se(IV) and Cr(VI), its elimination and application to Gerede river water

Trace chromium(VI) determination plays an important role since it is carcinogenic agent and toxic pollutant. For this purpose a direct method is developed using differential pulse polarography, DPP. When selenite was added into solutions of some ions such as copper(II), lead(II), cadmium(II), zinc(II), and chromium(VI) their DP polarographic peak decreased. This kind of interference will cause large errors in the determinations, its elimination is very important. The interference between selenite and Cr(VI) ions could be eliminated in B-R (Britton-Robbinson) buffer at pH 8.5. In this work the effect of components present in buffer has been investigated and it was found that phosphate and borate eliminated the formation of Cr–Se intermetallic compound formation. While it was possible to determine 1 × 10−5 M Cr(VI) in the presence of 100 times more selenite as (1.0 ± 0.1) × 10−5 M, in borate medium, it was possible to determine (1.0 ± 0.05) × 10−5 M in phosphate medium. In the presence of selenite detection limit (S/N = 3) was 9.0 × 10−8 M Cr(VI) by using either phosphate or borate This method was applied to Gerede river water, after oxidation all Cr(III) present into Cr(VI).