Determination of chromium(VI) and total chromium in water by in-electrode coulometric titration in a porous glassy carbon electrode

A poly(p-toluene sulfonic acid)-modified glassy carbon electrode showed an excellent electrocatalytic effect on the oxidation of dopamine (DA) and ascorbic acid (AA). Favorable electrostatic interaction between the negatively charged P-pTSA film and cationic species of DA or anionic species of AA may mainly contribute to the response of DA and AA at this electrode. In differential pulse votammetric (DPV) measurements, the poly(p-toluene sulfonic acid) film modified electrode can separate the DA and AA oxidation potentials by about 192 mV and can be used to the selective determination of dopamine in the presence of high concentration of ascorbic acid (e.g., 0.5 mmol L⁻¹) and the detection limit was 6.0 × 10⁻⁷ mol L⁻¹. The electrode shows excellent sensitivity, good selectivity and antifouling properties.