Abstract
The iodine content in food salt is generally determined qualitatively using rapid test kits or quantitatively by iodometric titration (reference method). Spectrophotometric analysis is one of the recent developed quantitative methods, which has the advantage of being simple, robust and more convenient for the laboratory technician. However, there are few comparative studies between this method and the reference method. The aim of this study was to evaluate the agreement between spectrophotometric and iodometric titration methods. From May to October 2013, 117 salt samples were collected in the households of Glazoué’s town (Benin), through a three-stage sampling. Samples were assayed by iodometric titration and by a portable spectrophotometer (WYD Iodine Checker). The agreement between results of the two methods was performed using Bland-Altman plots. The mean levels of iodine in salt samples were 28.2±14.0 and 28.4±14.0 ppm by iodometric titration and spectrophotometry respectively. There is an excellent correlation between the results of both methods (r= 0.97, p< 0.001). The agreement between the two methods gave a mean difference of d= 0.2 ppm, within the limits: d ± 2 sd= -6.2 and 6.5 ppm. This study showed that the spectrophotometric method can replace the iodometric titration for iodine analysis in dietary salt. This method is more convenient, uses simple laboratory procedures and can be popularized. Key words: Spectrophotometry, Iodometric titration, food salt, Iodine.
Highlights
The universal iodization of dietary salt is the least expensive and most effective strategy to prevent and control iodine deficiency disorders (Farebrother et al, 2015)
The concordance results between spectrophotometric and titration measurements by Bland-Altman plots were: d= 0.2 ppm, d±2 sdd= - 6.2 and 6.5 ppm, with a concordance coefficient: Intra-class correlation coefficient (ICC)= 0.9 (Figure 2)
The study results showed that the averages iodine contents in salts samples were 28.4±14.0 by spectrophotometry and 28.2±14.0 ppm by iodometric titration
Summary
The universal iodization of dietary salt is the least expensive and most effective strategy to prevent and control iodine deficiency disorders (Farebrother et al, 2015). In 2006, the majority of countries had a salt iodization program (UNICEF, 2008). The evaluation of effectiveness of these programs is based among other reasons, on the iodine determination of salt throughout the distribution chain and at the household level (Jooste and Strydom, 2010). Iodine content is determined by iodometric titration, the most common and most precise method. This method takes time for laboratory technicians normally spending an average of 20 min per one salt sample (Jooste and Strydom, 2010; Khazan et al, 2013; Zahidi et al, 2016)
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