Determination of Iodine in Seafood by Inductively Coupled Plasma/Mass Spectrometry

Abstract

A method was developed for determination of total iodine content in different standard reference materials (SRMs) and seafood products by inductively coupled plasma/mass spectrometry (ICP/MS). If iodine is present as iodide and nitric acid is used in the wet digestion system, the observed signal is not stable when iodine is measured by ICP/MS at m/z 127. To stabilize the iodine signal, 3% ammonia solution (1 + 1, v/v) was added to the digest. The limit of quantitation of the method, defined as 6 times the standard deviation in the blank solution (n = 20) was estimated to be 15 mg/kg (using 0.2 g dry mass and a dilution factor of 50). The precision, expressed as repeatability of the iodine concentration, varied between 3.2 and 12% in SRMs, with concentrations of 4.70–0.17 mg/kg dry matter. The described method was compared with a method using tetramethylammonium hydroxide extraction. Both methods showed good precision and trueness by analyses of SRMs. The 2 methods were used to determine iodine in seafood from the Barents Sea, the Norwegian Sea, and the North Sea. The results showed great variation between different fish species as well as between individuals within a species. The lowest values of iodine were recorded in muscle of ling (Molva molva) with a mean of 0.07 mg/kg fresh weight and a variation between 0.03 and 0.11 mg/kg fresh weight. The highest values were found in cod (Gadus morhua) from the Barents Sea, with a mean of 2.5 mg/kg and a variation between 0.7 and 12.7 mg/kg fresh weight.

A preliminary study on tailoring of fillet iodine concentrations in adult Atlantic salmon (Salmo salar L.) through dietary supplementation

“…Data from a Norwegian surveillance programme on commercial feeding stuffs for salmonids carried out in 2000 showed iodine concentrations in feeds ranging from 1.2 to 10.5 mg kg )1 dry weight with an average of 4.6 mg kg )1 (n ¼ 96). The substantial variation of iodine encountered in the commercial feeds is because of the great variation among species used for fish meal production (Julshamn et al 2001). The EU has authorized a maximum permitted level of inclusion for iodine in fish feed of 20 mg kg )1 (based on 880 g kg )1 dry weight, EC 1970); however, this maximum limit does not appear to be based on toxicological studies in fish.…”

“…The iodine content of the biological samples was determined by inductively coupled plasma-mass spectrometry (ICP-MS) (Perkin Elmer SCIEX Elan 5000A, Toronto, Canada). The method includes extraction with tetramethyl ammonium hydroxide prior to ICP-MS determination, which stabilizes iodine in the sample solutions (Julshamn et al 2001).…”

“…The iodine content varies widely from fish species to species and also among individuals, ranging from 0.03 to 12.7 mg kg )1 (Kidd et al 1974;Varo et al 1982;Wenlock et al 1982;Eckhoff & Maage 1997;Julshamn et al 2001;Rose et al 2001). Atlantic salmon is a fish species with a relatively low concentration of iodine in the fillet varying between 0.06 and 0.34 mg kg )1 wet weight, whereas Atlantic cod (Gadus morhua) caught in the Barents Sea ranged between 0.34 and 12.7 mg I kg )1 fillet (Julshamn et al 2001). As shown for selenium it may be possible to tailor salmon fillet concentration of iodine by dietary supplementation (Lorentzen et al 1994).…”

Effect of cultivated copepods (Acartia tonsa) in first-feeding of Atlantic cod (Gadus morhua) and ballan wrasse (Labrus bergylta) larvae

“…For iodine analyses, freezedried samples were wet digested by use of a microwave technique in nitric acid with 30% hydrogen peroxide and diluted to 25 mL (Julshamn et al 2000). The samples were then analysed by an Agilent 7500 inductively coupled plasma mass spectroscopy (ICP-MS) instrument with HP computer and Chem Station (Julshamn et al 2001).…”

Iodine content of cooked and processed fish in Turkey

“…The iodine content in fishes varies at high levels (Karl et al,2001(Karl et al, ,2005. Julshamm et al (2001) measured the iodine content in various fish species off the coast of Norway and from the North Sea. They found a great variation between different individuals of the same species as well as between different fish species.…”