Determination of chromium(VI) in the soil organic fraction

A procedure was developed for determining chromium(VI) in the soil organic fraction; it consisted of three steps: the preparation of a soil solution; the isolation and separation of chromium(VI) and chromium(III); and the determination of chromium(VI). Soil solutions were prepared by leaching soil samples with a Na4P2O7 solution (the Rudd method). Chromium(VI) was extracted from the soil solution with a solution of sodium diethyldithiocarbamate in n-amyl alcohol; the conditions of the extraction and separation of chromium(VI) and chromium(III) were optimized. Chromium(VI) in solutions was determined after back extraction by spectrophotometry with diphenylcarbazide or by flame atomic absorption spectrometry. The procedure was validated using a reference soil sample, and the material balance of chromium in the systems under study was calculated.