On-line oxidation of Cr(III) to Cr(VI) for use with the flow injection analysis technique

Abstract

An on-line procedure for the oxidation of Cr(III) to Cr(VI) was developed. The extent of oxidation was followed using the 1,5-diphenylcarbazide (DPC) spectrophotometric method accommodated in a flow injection analysis (FIA) system. Cerium(IV) sulphate and potassium peroxydisulphate were tested as oxidising agents. Despite the high oxidation power of the peroxydisulphate ion in acidic solution, the use of Ce(IV) is more convenient under dynamic conditions. The best experimental conditions were obtained at 45 °C using a 0.025%m/V Ce(IV) solution in 0.07 M H₂SO₄ with the Cr(III) solutions containing up to 3.0 × 10^–2M H₂SO₄.