Preconcentration and spectrophotometric determination of chromium (VI) and total chromium in drinking water by the sorption of chromium diphenylcarbazone with surfactant coated alumina

A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VE) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 mi of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO4. The relative standard deviation (10 replicate analyses) at the 10 mu g l(-1) of chromium (VI) and 10 mu g l(-1) of total chromium were 3.5 % and 3.4 % and corresponding limits of detection ( based on 3 sigma) were 0.040 mu g 1.1 and 0.033 mu g l(-1), respectively.