Determination of Cr(VI) in water samples by ICP-OES after separation of Cr(III) by montmorillonite

In the present work a simple method was proposed for the determination of Cr(VI) in water samples using a previous separation of Cr(III) by the low cost sorbent montmorillonite, followed by separation of the solid phase and subsequent quantification of Cr(VI) employing ICP-OES. A complete Cr(III) removal was observed after only 1 minute of contact time between 25 mg of the clay mineral montmorillonite saturated with potassium ions (MTK) and the aqueous sample. On the other hand, the Cr(VI) remained in solution, yielding a suitable separation of the species. The method presented appropriate accuracy and precision in comparison with the official method of diphenylcarbazide (DPC), showing a good performance for Cr(VI) quantification in effluent water samples, with 0.20 and 0.70 mu g L-1 for the Limit of Detection (LOD) and the Limit of Quantification (LOQ), respectively. Based on the experimental results, MTK showed remarkable characteristics to be used as a sorbent phase for an easy and fast separation of chromium species and consequently to provide the speciation analysis.