A Novel Modified Carbon Paste Electrode for the Determination of Chromium(III) in Water

Two kinds of modified carbon paste electrodes for chromium(III) ion based on zeolite as ionophore were prepared. 3-Methylpyrazol-5-one was used as modifier in sensor 1. Sensor 1 exhibits a Nernstian response for Cr(III) ions over a wide concentration range from 1 × 10–6 to 1 × 10–2 M with a slope of 19.8 ± 0.1 mV/decade. Sensor 2 was modified by using chlorinated multiwalled carbon nanotubes. This sensor shows a Nernstian response for Cr(III) ions over a concentration range from 1 × 10–7 to 1 × 10–2 M with a slope of 19.74 ± 0.1 mV/decade. Some parameters were optimized for the two sensors, such as pH of solution, composition of membrane and response time of electrode. The sensors were successfully applied to direct determination of chromium(III) in water samples and as an indicator electrodes in potentiometric titration of Cr(III) with EDTA.