Differential pulse polarographic determination of trace selenium(IV) and molybdenum(VI) using the catalytic hydrogen wave

In the presence of selenium(IV) and molybdenum(VI) a new polarographic peak appears which corresponds to a hydrogen catalytic wave. By differential pulse polarography a single, sharp peak at about −1.1 V is obtained, allowing trace determination of selenium(IV) and molybdenum(VI) in the range 1×10−6–5.0×10−9 M with a linear calibration and a detection limit of 1.5×10−9 M. The optimum conditions are found to be 0.1 M KNO3 and a pH of about 3.2 (Britton–Robinson buffer). There is no serious interference from some ions when present at 1.0–40 times that of molybdenum. At higher amounts of interfering ions the interference is eliminated by the addition of EDTA.