Electrochemical Monitoring of Iodine and Its Disinfection By-Products with Diamond Thin-Film Electrodes

We report on the use of electrically-conducting diamond thin-film electrodes for the detection of iodine and its disinfection by-products in water supplies. The phenolic byproducts, 2-iodophenol, 4-iodophenol, and 2,4,6-triiodophenol, were investigated. Cyclic voltammetry was used to study the oxidation reaction mechanism. Flow injection analysis with amperometric detection was employed to determine the detection figures of merit. Two types of diamond thin-film were evaluated: microcrystalline and nanocrystalline. Both diamond types yielded a sensitive, reproducible and stable response for the oxidative detection of 2-iodophenol and 4-iodophenol. For example, the linear dynamic range for the most common phenolic by-product, 2-iodophenol, was 5 orders of magnitude, the minimum concentration detected (S/N ≥ 6) was 0.44 ppb, and the response precision was ca. 4%. Diamond electrodes were also used for the reductive detection of iodine in water supplies and preliminary results are reported. The results demonstrate the applicability of diamond electrodes for electrochemical monitoring of organic and inorganic chemicals in water supplies.