VOLTAMMETRIC DETERMINATION OF TRACES OF CR(VI) AND TOTAL CHROMIUM USING CATALYTIC CURRENTS IN THE PRESENCE OF NITRATE

A sensitive voltammetric method for determinations of traces of Cr(VI) and total chromium was proposed. The method is based on the depositio n of elemental chromium from an ammonia buffer solution containing Cr( VI), its oxidation to Cr(III) and then reduction to Cr(II) in the pres ence of nitrate for amplification. The Cr(VI) was determined after add ition of Al(III) or Fe(III) to the sample solution before its alkalisa tion. The total chromium was determined after oxidation of Cr(III) to Cr(VI) under UV-irradiation. The calibration graph was linear between 5 x 10(-10) and 5 x 10(-9) mol l(-1) Cr(VI) at deposition time 300 s. The accuracy of the method was verified by the determination of chromi um in the reference material and river water samples spiked with a kno wn amount of Cr(VI).