Determination of Triiodide Ion Concentration Using UV-Visible Spectrophotometry†

The concentration of iodine species can be measured using several different analysis methods. One of the most wellknown methods involves iodine titration with a thiosulfate solution. Total iodine can be analyzed using spectrometry, such as inductively coupled plasma-atomic emission spectrometry (ICP-AES), atomic absorption spectrometry (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS). As elemental iodine has various valance states, various stable iodine species are present in aqueous solutions. Stable iodine species can include iodide ions, triiodide ions, iodine and iodate ions. For the quantitative analysis of these species, ion chromatography (IC) has been used in analytical laboratories. In addition, ultraviolet-visible spectrophotometry and Raman spectrometry have been used for the speciation and quantitative analyses of iodine species. Recently, after the severe accident at the Fukushima nuclear power plant in Japan, the chemical behaviour of radioactive iodine received increased attention as a result of interest in evaluating the volatility of iodine species, which depends on the chemical conditions of the exposed environments. The use of γ-ray spectroscopy to measure radioactivity is the best method for determining radioactive iodine concentrations. However, to use radioactive iodine, a licensed Determination of Triiodide Ion Concentration Using UV-Visible Spectrophotometry†