Solid-phase spectrophotometric iodometric determination of iodate in food salt using а polymethacrylate matrix

A sensitive solid-phase spectrophotometric method for the quantitative determination of iodate in iodized salt samples using a polymethacrylate matrix is proposed. The procedure is based on the reaction of iodate with excess iodide in the acidic medium (pH 1-2) with the release of free iodine in the amounts equivalent to the iodate to be determined, the extraction of the iodine formed with a polymethacrylate matrix, and the absorbance measurement of the matrix at 365 nm. The developed procedure ensures the determination of 0.2–3.6 mg/L of iodate with limits of detection of 0.03. The effect of interfering ions, that might be present in the table salt samples, on the determination of iodate is also investigated. It is shown that Ca(II), Mg(II), К + , Na + , Cl - , SO 4 2- do not interfere with the determination of iodate. However, Fe(III) causes serious interference, and the addition of fluorides is required to mask iron up to 20-fold. The proposed method has been successfully applied for the determination of iodate in salt samples. The iodate contents thus determined in the iodized salt samples by the solid-phase spectrophotometric method were compared with the total iodine determined in the salt samples by iodometric titration according to GOST 51575. The solid-phase spectrophotometric method for iodate determination in salt samples has advantages over the iodometric titration, for example the increased sensitivity, simplicity and speed of the analysis. Тhe applicability of the polymethacrylate matrix as the final analytical form for the rapid visual iodate test is shown. Keywords: iodate, iodometry, polymethacrylate matrix, solid-phase spectrophotometry, visual test determination (Russian) DOI: http://dx.doi.org/10.15826/analitika.2018.22.1.009 D.A. Fedan 1 , N . V . Saranchina 2 , N.A. Gavrilenko 1 , M.A. Proskurnin 3 1 National Research Tomsk State University, pr. Lenina, 36, 634050, Tomsk, Russian Federation 2 National Research Tomsk Polytechnic University, pr. Lenina, 30, Tomsk, 634050, Russian Federation 3 M.V. Lomonosov Moscow State University, Leninskie Gory, GSP-1 Moscow, 119991, Russian Federation