Electrochemical detection of Cr(VI) and Cr(III) ions present in aqueous solutions using bio-modified carbon paste electrode: a voltammetric study

Chromium is recognised as a potent water pollutant by the WHO and thus it becomes pertinent to continuously monitor chromium levels in the waterbodies. Voltammetry, an electroanalytical technique, has been utilised for the detection of hexavalent (Cr(VI)) and trivalent (Cr(III)) chromium in aqueous samples. Carbon Paste Electrode (CPE) modified using Sphingopyxis macrogoltabida SUK2c, an indigenous bacterial strain isolated from the water samples collected from Sukinda Valley, Odisha, India, was used as a working electrode in a typical three-electrode electrochemical cell. The developed biosensors were found to provide about 3.5 fold increase in cathodic peak current compared to the bare CPE for Cr(VI) ions. Using cyclic voltammetry (CV), the Lowest Limit of Detection (LLOD) of 1 x 10(-4) M and 1 x 10(-2) M for Cr(VI) and Cr(III) ions, respectively, were achieved with the biosensors. The LLOD was further improved to 1 x 10(-9) M and 1 x 10(-7) M for Cr(VI) and Cr(III) ions, respectively, adopting differential pulse cathodic stripping Vvoltammetry (DPCSV) technique employing the biosensors. The concentrations of Cr(VI) and Cr(III) ions present in water samples collected from Sukinda Valley, Odisha, India, could be determined using the biosensor. The plausible mechanisms involved in the detection of Cr(VI) and Cr(III) ions by the developed electrochemical biosensor are discussed.

Automated summary

This study developed a biosensor for the detection of hexavalent and trivalent chromium in water samples using the electroanalytical technique of voltammetry. With a modified carbon paste electrode as the working electrode, the biosensor achieved high sensitivity and low detection limits.