A highly sensitive and selective electrochemical sensor for determination of Cr(VI) in the presence of Cr(III) using modified multi-walled carbon nanotubes/quercetin screen-printed electrode

• A novel screen-printed carbon electrode modified with quercetin/multi walled carbon nanotubes was fabricated.
• Determination of Cr(VI) in the presence of excess of Cr(III) was performed without any pretreatment.
• The method is based on electroreduction of quercetin–Cr(III) complex to quercetin–Cr(II) complex
• Quercetin–Cr(III) complex generated in situ from Cr(VI) accumulated at the electrode surface.
• The developed sensor was used for the determination of Cr(VI) in drinking water samples.

A novel screen-printed carbon electrode modified with quercetin/multi-walled carbon nanotubes was fabricated for determination of Cr(VI) in the presence of excess of Cr(III) without any pretreatment. The method is based on accumulation of the quercetin–Cr(III) complex generated in situ from Cr(VI) at the modified electrode surface in an open circuit followed by differential pulse voltammetry detection. The new method allowed selective determination of Cr(VI) in the presence of Cr(III). The influence of various parameters affecting the adsorptive stripping voltammetry performance was investigated. Under the optimum conditions, the calibration plot was found to be linear in the Cr(VI) concentration range from 1.0 to 200 μmol− 1 with a limit of detection(S/N = 3) of 0.3 μmol L– 1. The relative standard deviation (RSD%) of seven replicates of the current measurements for a 50 μmol− 1 of Cr(VI) solution was 3.0%. The developed electrode displayed a very low or no sensitivity to alkali, alkali-earth and transition metal cations and was successfully applied for the determination of Cr(VI) in drinking water samples.