Determination of Iodine in Foods by High Performance Liquid Chromatography with Electrochemical Detection

An HPLC-ECD (electrochemical detector) method for determination of low levels of iodine in foods was developed. As compared with a conventional GC-ECD (electron capture detector) method, the proposed method is simpler and easy to use. Each sample was treated with 4N KOH and 25% KNO3, and pre-incinerated by gently heating at approx. 100°C. Then it was completely incinerated at 550°C for 5 hours in an electric furnace. Iodine was extracted from the incinerated sample by ultrasonic extraction with distilled water. Twenty microliters of the extractant was used for HPLC analysis. Conditions of HPLC were as follows: column, Shodex IC-524A; eluent, 100mM NaH2PO4 containing 5mM ethylenediamine; flow rate, 1.5ml/min; detector, ECD (working electrode, Ag; applied voltage, 60mV vs. Ag/AgCl). The determination range was between 0.005 and 0.1μg/g. Recoveries and repeatabilities on dairy and other foods were more than 95% and 2-3% as coefficient of variation (CV), respectively. The proposed method should be useful for iodine determination in many kinds of foods.