Determination of hexavalent chromium is essential for disposal of chromium-containing waste into the environment, but current methods produce ambiguity in reported results. Using five concentration levels of Cr(III) and spiking with three concentrations of Cr(VI), determinations of Cr(VI) were made using EPA** solid waste methods 7197 (Coprecipitation), 7197 (Colorimetric-Dephenylcarbazide), and 7197 (Chelation-Extraction). The data indicate limitations in quantifying Cr(VI) in Cr(III) matrices. The Coprecipitation method was shown to be inadequate in determining the presence of Cr(VI) in Cr(III) matrices. Chelation-Extraction was able to show that one Cr(III) solution was free of any Cr(VI) contamination. For the other Cr(III) solution, the method indicated a presence of Cr(VI) but was unable to quantify the amount. Colorimetric analysis proved to be the most reliable, consistent, and informative of all three methods. It confirmed the findings of the Chelation-Extraction method and, in addition, quantified the amount of Cr(VI) present in the Cr(III) solution.
