Speciation of Chromium after Coprecipitation with Cu-Violuric Acid and Determination by Flame Atomic Absorption Spectrometry

A method based on coprecipitation of Cr (III) with copper-violuric acid for the preconcentration/speciation of Cr (III) and Cr (VI) has been developed. While Cr (III) was quantitatively recovered, Cr (VI) was recovered under 15 % level at pH 6. Total Cr was determined with reducing of Cr (VI) to Cr (III) with concentrated sulphuric acid and ethanol. The concentration of Cr (VI) was calculated by the concentration difference between the total Cr and Cr (III). The influences of analytical parameters such as pH, amount of coprecipitant, sample volume were examined. The detection limit was obtained as 1.17 mu g L-1 for Cr (III). The accuracy of presented method was checked by analyte addition and analysis of certified reference materials. The method for determination with atomic absortion spectrometry after preconcentration with coprecipitation of Cr (III), Cr (VI) and total Cr has been applied to tap water, waste water and soil samples.