Determination of iodides in water samples with high chloride content by in-built-electrode coulometric titration using a porous carbon electrode

The work describes the determination of iodides using in-built-electrode coulometric titration using a flow-through system. The principle of determination consists of electrochemical generation of iodine from iodides within the electrode and subsequent reduction of the generated iodine to iodide. The measurements were performed in a thin-layer arrangement of porous glassy carbon electrode inserted into an electrochemical cell. A mixed carrier electrolyte solution composed of 0.1 mol L −1 sulfuric acid and 0.001 mol L −1 hydrochloric acid was used. The method provides a large linear range from 0.1 to 40 mg L −1 with R 2 = 0.9993. The calculated LOD and LOQ were 0.03 mg L −1 and 0.09 mg L −1 , respectively. Repeatability was evaluated by successive measurements, and the relative standard deviation was lower than 0.54%, attesting to good precision. The procedure was tested by analyses of bottled mineral water samples, natural mineral water samples, one seawater sample and iodized table salt sample. A good agreement with the standard addition technique was achieved for all samples.