A coprecipitation method has been established for speciation of chromium(III) and chromium(VI) in real samples. The procedure is based on the coprecipitation of Cr(III), by using a new organic coprecipitant, 3-phenyl-4-o-hydroxybenzyl-idenamino-4,5-dihydro-1,2,4-triazole-5-one, without adding any carrier element. After reduction of Cr(VI) by concentrated H2SO4 and ethanol, the method was applied to the determination of total Cr. The level of Cr(VI) was calculated by the difference of total Cr and Cr(III) levels. For optimum recovery of Cr(III), different analytical factors such as pH, amount of coprecipitant, centrifugation rate and time, and effect of sample volume, were investigated. The influences of some anions, cations, and transition metals on the recoveries were also investigated, and no significant interferences were observed. The preconcentration factor was 100. The detection limit based on 3 times standard deviation (sigma) of the blank (n = 10) for Cr(III) was 0.50 microg/L. In order to evaluate the accuracy of the method, certified reference materials (CRM-TMDW-500 Drinking Water and National Institute of Standards and Technology Standard Reference Material 1573a Tomato Leaves) were analyzed, and the results obtained were in good agreement with certified values. The presented procedure was applied for Cr speciation in various solid and liquid samples with successful results.
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