Determination of extractable chromium(VI) in the presence of large excess of chromium(III) in solid materials

A method for the determination of chromium(VI) in solid materials with a Cr(VI) content at ppm level in the presence of ca. 10% Cr(III) has been devised. Chromium(VI) is extracted with 0.1M NaOH in a double-water bath (97° C) for 90 min. Differential-pulse polarography in 1M NaOH and spectrophotometry with 1,5-diphenylcarbazide have been tested for use in the final determination of Cr(VI). After extraction in the form of dithiocarbamate into methylisobutylketone or ethylacetate, chromium was determined by flame AAS and DPP in an organic extract.