Protocol For The Determination Of Total Iodine In Iodized Table Salts Using Ultra High-Performance Liquid Chromatography

Background/Objectives: Potassium iodate and potassium iodide were commonly fortified in iodized table salt, where continuous monitoring is needed to maintain the quality. Our study reported an optimized detection method for total iodine in iodized table salt using 0.5 M sodium bisulfite as reducing agent; Methods: The iodized table salt (0.5 g) was dissolved in 0.5 M sodium bisulfite solution prior to injection in ultra high-performance liquid chromatography (UHPLC) coupled with diode array detector using weak anion-exchange column (2.1 mm×150 mm, 5 μm); Results: Iodide was eluted at 9.92±0.06 minutes (λ=223 nm) when isocratic mobile phase of 1:1 (v/v) methanol:120 mM phosphate buffer mixed with tetrasodium pyrophosphate (pH 3.0) was running at 0.20 mL/min (15 minutes). Iodide detected as total iodine from 10 to 60 mg/Kg with limit of detection (LOD) 1.2 mg/Kg and limit of quantification (LOQ) 3.7 mg/Kg. The method was validated with relative standard deviation (RSD) of 4.2%, 0.4%, 1.6%, 0.8% for accuracy, repeatability, intermediate-precision and robustness, respectively. The determination of total iodine was successful on six (6) samples (n=3), which recovered 87.2%-106.9% of iodate and iodide spike; Conclusions: Thus, the study provided a validated protocol for the determination of total iodine in iodized table salt using 0.5 M sodium bisulfite.