Rapid Determination of Inorganic and Organic Iodine in Edible Salt and Kelp Samples by a Z-Ⅱ Iodine Probe

Abstract

BACKGROUND At present, iodine content in edible salt and kelp products is mainly determined as the form of total iodine content, but the speciation analysis of inorganic iodine and organic iodine mainly relies on the hyphenated techniques of large-scale instruments. OBJECTIVES To establish the determination method of iodine content in edible salt and kelp as well as the digestion method for the organic iodine in the closed PTFE bomb. METHODS Rapid determination of inorganic and organic iodine content in edible salt and kelp products by using crystal membrane electrode technique with a solid-state and no internal reference liquid crystal film electrode (Z-Ⅱ iodine probe) developed by silver sulfide iodide method, combined with PTFE bomb microwave digestion technique. RESULTS Table salt contained 20mg/kg of inorganic iodine, and 2mg/kg of organic iodine. The concentration of organic iodine was 2.9×103mg/kg in kelp. The linear correlation of inorganic and organic iodine contents in the range of 10-100mg/kg was good. The standard-addition recoveries were 97.1%-101.0%, and the detection limit was up to 1mg/kg. This method was applied to the determination of iodine content in actual edible salt and kelp on the market, the relative standard deviation of inorganic and organic iodine in the samples was less than 0.92% and 4.20%, respectively. The analytical results were in agreement with those of the national standard method and ultraviolet spectrophotometry method, which indicated that the established method was reliable. CONCLUSIONS The analytical method has the advantages of low reagent consumption, low cost and convenient operation, which can be used for the determination of inorganic and organic iodine contents.

Keywords

• probe
• rapid determination
• organic iodine
• inorganic iodine
• edible salt
• kelp