Indirect determination of hexavalent chromium ion in complex matrices by adsorptive stripping voltammetry at a mercury electrode.
A sensitive method for the determination of chromium ion(VI) in complex matrices such as crude oil and sludge is presented based on the decreasing effect of Cr(VI) on cathodic adsorptive stripping peak height of Cu-adenine complex. Under the optimum experimental conditions (pH 7.5 Britton-Robinson buffer, 5x10(-5)M copper, 8x10(-6)M adenine and accumulation potential -250mV versus Ag/AgCl), a linear decrease of the peak current of Cu-adenine was observed, when the chromium(VI) concentration was increased from 5mugL(-1) to 120mugL(-1). Detection limit of 2mugL(-1) was achieved for 120s accumulation time. The relative standard deviations (R.S.D., %) were 1.8% and 4% for chromium(VI) concentrations of 18mugL(-1) and 100mugL(-1), respectively. The method was applied to the determination of chromium(VI) in the presence of high levels of chromium(III), in various real samples such as crude oil, crude oil tank button sludge, waste water and tap water samples. Effects of foreign ions and surfactants on the voltammetric peak and the influences of instrumental and analytical parameters were investigated in detail. The accuracy of the results was checked by ICP and/or AA.
Safavi
A
A
Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran.
Maleki
N
N
Shahbaazi
H R
HR