Enhancing instrumental sustainability: a spectrophotometric approach for quantifying iodate in nutritionally significant salts through the adaptation of the classical iodometry method

With the primary objective of transitioning from the classical iodometric method to an instrumental approach, preserving precision in the analytical process, this study presents the development of a spectrophotometric method for quantifying iodate (iodine equivalent) in nutritionally significant salts. Therefore, the wavelengths of maximum absorption of the I3- (350.8 nm) and I3-starch (574.1 nm) complexes were determined. The complexes demonstrated stability, as indicated by the respective molar extinction coefficient values (ε) obtained over the course of the reaction time (measured up to 1h, at 5-minute intervals, and at 28°C), for concentrations ranging from 7.81×10-6 to 1.25×10-4 mols/L of KIO3. A linear correlation between concentration and absorbance was established within the specified concentration range, with detection and quantification limits defined as 0.09 and 0.29 mg/L (350.8 nm) and 0.13 and 0.39 mg/L (574.1 nm), respectively, and calculated recovery of 102.9%. The reproducibility of the method was assessed by varying the analyst, the equipment, and the analysis day. Using the developed method, it became feasible to quantify the elemental iodine equivalent in three commercially available salts commonly employed for food purposes. When compared to the classical/traditional iodometric method, the spectrophotometric method for quantifying iodate in salts showcases sustainability with minimized solvent and reagent usage, reduced waste generation, shorter analysis time, and lower sample requirements, aligning with environmentally conscious analytical practices.