Microdetection of Chromium Mixed–Valences using CuNi/Ti Electrode and Linear Sweep Voltammetry

An electrode of non-precious metal has the potency to be utilized as a working electrode for voltammetry measurements of Cr3+ and Cr6+.  The analytical performance of the electrode in determining specific metal species qualitatively and quantitatively was studied. The detection data were recorded and analyzed using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), whereas scanning electron microscope (SEM) and X-ray diffraction (XRD) spectroscopy were used to determine the surface morphology and the presence of crystalline in the electrode. Electroanalytical performance was determined by linear sweep voltammetry. The results show that the reduction of Cr6+ to Cr3+ appeared at +0.84 V (vs Ag/AgCl) and the reduction of Cr3+ to Cr2+ at +0.74 V             (vs Ag/Ag).  The optimum conditions for measuring Cr3+ were found at pH 6, deposition time of 30 seconds, and a scan rate of 160 mVs-1. The optimum pH for measuring Cr6+ is 4, deposition time of 60 seconds, and a scan rate of 140 mVs-1. The regression curve for the Cr3+ is linear in concentration 1 – 10 gL-1 with a correlation coefficient of  0.9883 and a detection limit of 2.08 gL-1. While the Cr6+ is linear in the range of 1 – 10 gL-1 with a correlation coefficient of 0.99 and a detection limit of 2.18 gL-1. There is a slight difference in the individual measurement current and the mixture of Cr3+ and Cr6+ but with a good agreement for the oxidation-reduction potential. The measurement data analysis shows the feasibility of the electrode and the measurement system developed.