Amperometric Sensor Based on Au/MWCNT for Simultaneous Speciation of Cr(III) and Cr(VI) Ionic Species

Abstract

In this paper, the simultaneous speciation of the Cr(VI) and Cr(III) ionic species in aqueous solutions was achieved by measuring the current of a cyclic voltammogram at determined potential, under mass transport limiting conditions, using a rotatory disk electrode. The influence of the sensor interface, the rotation speed, and the scan rate potential on the sensitivity and time analysis was studied. Quantification of Cr(III) is related to the oxidation process to Cr(VI), while quantification of Cr(VI) is associated to reduction process to Cr(III). From the analysis of cyclic voltammograms at different rotation rate and scan rate, were determined that Cr(III) is controlled by electric charge transference, on the other hand, Cr(VI) is controlled by mass transference. The sensor was modified with ultra-low loading of Au nanoparticles on the carbon nanotubes (CNT), whose improve the quantification of Cr(VI) and Cr(III) compared with the conventional materials.