A New Analytical Method for Measuring Total Iodine Content in Fish for the Standard Tables of Food Composition in Japan

摘要

The standard method prescribed in the Analytical Manual of the Standard Tables of Food Composition in Japan for measuring total iodine is not always applicable to fish, particularly when they contain large amounts of lipophilic iodine compounds. In this study, we developed a new analytical method with alkaline-ashing followed by ICP-MS (AA-ICP-MS) to cover this shortcoming in the standard method. The fish samples were ashed with potassium hydroxide and iodine was subsequently extracted with water from the ash; iodine content was then determined by ICP-MS. A single-laboratory validation of the AA-ICP-MS method showed recoveries ranging from 85 +/- 9 % to 96 +/- 7 %, and the difference between certified and determined values was not significant. Furthermore, both of the repeatability and intermediate precision in the RSD are 7.7 %, with a quantification limit of 0.20 mg/kg. Based on these results, we suggest that this AA-ICP-MS method represents a superior supplementary method for the Analytical Manual to determine 0.20 mg/kg and more of total iodine specifically in fish.