Quantification of Hexavalent Chromium in Surface Water Samples by a Selective Electrochemical Method

The current study aimed to develop a robust, selective, and sensitive voltammetric method for hexavalent chromium (Cr-VI) at a chemically modified carbon paste electrode. For the preparation of the electrode, a micropipet tip was packed with modified carbon paste mainly consisting of graphite powder and diphenylcarbazone (5 + 1, w/w). Voltammetric mode, type of electrolyte, pH, volume of electrolytes, accumulation time, accumulation potential, and stirring rate were studied in detail. The current response was linearly dependent on the concentration of Cr-VI from 0.20 to 2.60 mu mol/L. The reproducible results were obtained for replicate analyses (n = 11) of three proposed electrodes of the same composition with RSDs of <2.0%. The LODs and LOQs were found to be 0.052 and 0.174 mu mol/L, respectively. The noticeable electrode surface passivation was not observed for the detection of Cr-VI. The proposed methods were successfully applied for Cr-VI in different surface waters in Sindh, Pakistan.