A rapid assessment method for determination of iodate in table salt samples

Digital colorimetric sensor for assessment of iodate in food-grade salt based on paper-based analytical device

A digital colorimetric sensor was developed for the on-site measurement of iodate in food-grade salt. It involved a paper-based analytical device (PAD) containing an immobilized iodide/starch reagent and a smartphone as the detection system. Iodate ions produce a blue-black coloration on the PAD, the smartphone captures a digital image of the PAD, and an installed mobile app performs an analysis to generate color values related to the intensity of the color in the PAD. Parameters in the image acquisition and PAD preparation were optimized, and a matrix-matched calibration plot was employed for quantification. The plot exhibited a linear response in the concentration range of 10 to 100 mg iodate kg^-1 of salt, and a detection limit of 2.20 mg kg^-1 was determined. The present method was applied to analyze real samples, and the results agreed well with those obtained using the reference method at the 95% confidence level.

Smartphone-based optical transduction for the rapid microscale assessment of iodate in table salt

The measurement of iodine in table salt is vital for the successful implementation of the universal salt iodization (USI) program to fight iodine deficiency disorders (IDDs). This paper presents a smartphone-based optical transduction system for iodine measurement in table salt. The method was based on the response in the blue color space generated by the complex formed between the starch/iodide reagent and iodate in the salt sample. The parameters for the color reaction and for the image capture affected the response and were optimized. A matrix effect caused by NaCl was observed and was eliminated through matrix matching by incorporating NaCl in the standard solutions. The optimized method yielded a highly linear response to iodate concentrations ranging from 10 to 160 mg kg^-1 (r = 0.9993) with a limit of detection of 2.8 mg kg^-1. The method exhibited good accuracy and precision, based on AOAC standards. It produced results that were in agreement with those obtained using the reference method at the 95% confidence level. The smartphone performs optical transduction, as well as signal processing, to yield a display of the iodate concentration in the salt sample. The use of smartphones presents a simple, inexpensive, portable, and widely available device for on-site analysis of iodate in table salt.

Smartphone digital image colorimetry combined with solidification of floating organic drop-dispersive liquid-liquid microextraction for the determination of iodate in table salt

Smartphone digital image colorimetry (SDIC), combined with solidification of floating organic drop-dispersive liquid-liquid microextraction (SFOD-DLLME), was proposed for the determination of iodate ions. A colorimetric box was designed to capture images of sample solutions. Factors affecting the efficiency of SDIC included type of phone, region of interest, position of camera, and distance between camera and sample solution. Optimum SFOD-DLLME conditions were achieved with 1-undecanol (500 µL) as the extraction solvent, ethanol (1.5 mL) as the disperser solvent within 20 s extraction time. Limit of detection (LOD) was found as 0.1 µM (0.2 µg g^-1) and enrichment factors ranged between 17.4 and 25.0. Calibration graphs showed good linearity with coefficients of determination higher than 0.9954 and relative standard deviations lower than 5.6%. The proposed method was efficiently applied to determine iodate in table salt samples with percentage relative recoveries ranging between 89.3 and 109.3%.