Determination of dissolved inorganic species of iodine by spectrophotometric titration

Abstract

A method for determining iodate and iodine(+1) in aqueous solutions is proposed. The assay is similar to a previously described method for the determination of iodide and iodine(0), which were titrated with standard iodate in hydrochloric acid solution. A sample solution made 0.5–1.5 M in hydrochloric acid is titrated with a standard iodide solution and monitored spectrophotometrically at 230 nm. The species involved have strong absorbances that are well differentiated at this wavelength. By combining the two titrations it is possible to resolve any mixture of species of iodine in different oxidation states. The precision of the method (standard deviation) is the same both when determining a single species (IO^–₃, I⁺, I₂ or I^–) and a mixture, and is equal to 2 × 10^–7M. Chloride and bromide, even at very high concentrations, do not interfere.