Selective voltammetric determination of chromium (VI) with DTPA and nitrate

A voltammetric determination of Cr(VI) in a flow system is described based on the selective accumulation of the reduction product of Cr(VI) on an HMDE, its complexation with DTPA and subsequent reduction of the complex in presence of nitrate. The calibration graphs were linear up to 100 and 5 nmol/L for deposition times 120 and 600 s, respectively. The relative standard deviation was 2.8% (n = 5) for Cr(VI) concentrations of 5 × 10^–8 mol/L. The detection limits (3 σ) for Cr(VI) were 1.0 and 0.12 nmol/L at deposition times of 120 and 600 s, respectively. Typical interferences derived from real water samples are discussed. The method has been applied for the determination of Cr(VI) in spiked natural water samples. Received: 18 June 1998 / Revised: 28 September 1998 / Accepted: 5 October 1998