A sensitive sequential non-chromatographic speciation analysis of chromium in natural/wastewaters by inductively coupled plasma optical emission spectrometry

A highly sensitive and novel sequential non-chromatographic speciation procedure has been developed for selective pre-concentration and separation of Cr(III) and Cr(VI) from natural and wastewaters. In this procedure, Triton X-114 micelle and cetylpyridinium bromide-Triton X-114 mixed-micelle are used sequentially for the extraction of hydrophobic Cr(III)-trifluoropentanedione and hydrophilic Cr(VI), respectively. Inductively couple plasma optical emission spectrometry (ICP-OES) is used for its determination. The parameters affecting the extraction process are optimized. Under the optimized conditions, the pre-concentration factors obtained are 50 and 15 while limits of detection (LOD) are 0.02 and 0.05 ng mL(-1) for Cr(III) and Cr(VI), respectively. These LODs are better than those of IC-ICP-MS and comparable to those of IC-ICP-DRC-MS methods. The recoveries are in the range of 95 to 99% at 10 to 40 ng mL(-1) with relative standard deviation of 2-4%. The accuracy of the procedure is validated by comparing the sum of the concentrations of each individual chromium species obtained from sequential extraction with total chromium in BCR certified reference materials such as Effluent-713, Influent-714 and Industrial effluent-715. The method was then applied to various water samples collected locally.