Iodine-starch reaction renewed: determination of iodate in table salts via the lab-in-syringe technique

Abstract

A novel in-syringe automated method was developed for simple, sensitive, and green determination of iodate in table salts. It is based on iodine–starch complexation as an environmentally benign and economic approach. Triiodide is generated in the acidic buffered sample from iodide. Embedding it in the amylose helix resulted in a steel-blue-colored complex, which was spectrophotometrically measured at 600 nm. Step-by-step addition and mixing of a reductant, acid, and soluble starch to the sample were carried out in the void of an automated syringe pump. Essential experimental parameters were fine-tuned to optimize method sensitivity and linearity of response. A limit of quantification of 0.4 µmol L⁻¹ (50 µg L⁻¹) iodate and a sampling frequency of 13 h⁻¹ were achieved. Linearity of calibration was confirmed between 1.5 µmol L⁻¹ to at least 10 µmol L⁻¹ with possible straightforward working range extension by in-syringe sample dilution. The determination of iodate content in table salts was precise with relative standard deviation values of <1.8% and accurate with a mean analyte recovery of 98.4 ± 3.8% studied at 2 and 5 µmol L⁻¹ levels. Noteworthy advantages are high method robustness, safe reagent manipulation, and a greenness score of 0.7 based on the AGREE metric tool, comparable to or surpassing those of formerly reported spectrophotometric methodologies (non-automated and flow-based). The developed method was a convincing, quick, and simple option to the existing protocols for iodate determination in commercial salts.