Assessment of Iodate in Food-grade Salt Based on a Smartphone Colorimetric Platform

Abstract

The regular monitoring of iodized salt available in the household and marketplace is necessary for the effective implementation of the national program of salt iodization to control iodine deficiency and its associated diseases. This study describes a colorimetric measurement of iodate in table salt using a smartphone equipped with applications for color analysis and direct readout of iodate levels. The method involved the measurement of the blue component of the colored solution under controlled lighting conditions. The parameters for colorimetric reactions were optimized using a univariate approach – including KI concentration, pH, type and volume of acid, and order of addition of reagents. The effect of NaCl and sample size on the B signal was also investigated. Under optimum conditions, a linear response was observed from 10 to 175 mg iodate per kg of salt (r = 0.9959) with a coefficient of variation of 1.9% over this range and a detection limit of 2.7 mg kg–1 salt. The method was applied for real samples, and the results agreed well with the reference method at the 95% confidence level. The simplicity of operation, compactness, and wide availability of smartphones offer a convenient colorimetric platform for the iodate assessment in table salt.