Electroanalytical Determination Of Chemical Oxygen Demand On Pbo2 - Bi Electrode

The chemical oxygen demand (COD) was determined using an electrochemical method based on electrolysis in a thin layer condition. Miniaturized electrodes of screen-printed graphite modified by PbO2-Bi electro-deposition were used for the application of exhaustive electrolysis in samples with volume in the order of microliters. The COD calibration protocol was established on the basis of the electrical charge transferred during electrolysis of standard solutions of organic compounds of interest. The response was evaluated with respect to the concentration of potassium hydrogen phthalate used as standard, the electrode potential, the concentration of chloride ions as typical interference, and the response of a typical industrial effluent. Experimental conditions were identified for high precision determinations with deviations of 5 % in all cases, and relative error between 1 and 6 %. The proposed method is capable of reproducing exact and accurate values of COD, when compared to the traditional method based in oxidation with H2SO4 and K2Cr2O7, demonstrating that electrochemical oxidation under thin layer condition, is a convenient method to determine the COD of aqueous solutions.