Sequential Spectrophotometric Determination of Trace Amounts of Periodate and Iodate in Water Samples after Micelle-Mediated Extraction

A cloud point extraction process using the nonionic surfactant Triton X-114 for extraction and pre-concentration of periodate and iodate ions from aqueous solution was investigated. The method is based on the extraction of triiodide ion, the colored product of the reaction of periodate and iodate with iodide in acidic media. The triiodide was concentrated in surfactant rich phase and then determined spectrophotometrically at 358 nm. For the determination of periodate and iodate in mixture, two sets of conditions were established. In one set of conditions only periodate reacted with iodide but in the other set both ions reacted with iodide. The data were evaluated by the method of proportional equations. The optimal extraction and reaction conditions (e.g., surfactant and reagent concentrations and centrifuge time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor, and enhancement factors) were obtained. Under the optimized conditions, the methods allowed the determination of periodate and iodate at concentrations between 2.0 and 1000 and 4.0 and 400 ng/mL, respectively. The proposed method was successfully applied to the determination of periodate and iodate in water samples.