The objective of the research effort was to experimentally assess the chemical behavior of the stable species of chromium during the preparation, chemical manipulation, and spectrophotometric analyses of simulated and authentic environmental samples for hexavalent chromium. The diphenylcarbazide colorimetric method was found to be specific and sensitive for Cr(VI), as either dichromate or chromate, in simulated aqueous solutions containing up to 1000-fold ratios of Cr(III). Problems of reduction were encountered with the method for analyses of simulated samples containing excesses of both Cr(III) and sulfide. Studies of selected digestion methods for the analyses of insoluble chromates revealed that the alkaline digestion generally provided satisfactory recoveries of Cr(VI) however, the nitric acid digestion was inadequate for the conditions studied. Although Cr(VI) spikes were stable in alkaline digests of most of the environmental samples studies, Cr(III) spikes were found to be partially oxidized in the alkaline digests, resulting in positive errors by as much as 100% in Cr(VI) measurements.

Draft final report Bibliographical references: leaf 112. Battelle Laboratories for the U.S. Environmental Protection Agency. Contract Number: 68-03-3224 Print reproduction.