title: Iodine determination in food samples using inductively coupled plasma isotope dilution mass spectrometry.
abstract: Two different sample treatment methods are used in connection with inductively coupled plasma isotope dilution mass spectrometry for accurate and precise determinations of iodine traces in food samples. 129I-enriched iodate is applied as a spike compound for the isotope dilution step. Extraction of iodine by tetramethylammonium hydroxide (TMAH) solution at high temperatures in a closed vessel is one of the sample treatment methods. The other one is a complete decomposition of the sample with a mixture of perchloric acid and nitric acid using microwave assistance. By analyzing different certified reference materials (three milk powders with different iodine levels, BCR CRM 63, 150, and 151; bovine liver BCR CRM 185), the accuracy of ICP-IDMS with both sample treatment methods could be demonstrated. The relative standard deviation was typically in the range of 0.6-2.8% for iodine concentrations between 0.1 microgram g-1 and 5 micrograms g-1. The detection limit was 8 ng g-1 using sample weights of 0.8 g. In a round robin test, using two different types of infant food samples, the results of the two ICP-IDMS methods and of an ICP-MS method without the isotope dilution technique, but applying the TMAH extraction procedure, agree very well with the mean of results of all participating laboratories also using ICP-MS/TMAH. However, the ICP-IDMS method is faster, more precise, widely independent of matrix effects, and, therefore, relatively accurate, which makes this method especially attractive for use as a routine method.
authors.affiliation: Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Rädlinger
authors.forename: K G
authors.initials: KG
authors.lastname: Heumann
mesh_terms: D000818:Animals; D002417:Cattle; D003611:Dairy Products / Q000032:analysis*; D006801:Humans; D007225:Infant Food / Q000032:analysis*; D007231:Infant, Newborn; D007452:Iodates / Q000032:analysis; D007455:Iodine / Q000032:analysis*; D007457:Iodine Radioisotopes; D008099:Liver / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D008872:Microwaves; D008892:Milk / Q000737:chemistry*; D017942:Nitric Acid; D010472:Perchlorates; D000644:Quaternary Ammonium Compounds; D011865:Radioisotope Dilution Technique; D015203:Reproducibility of Results
chemical_list: D007452:Iodates; D007457:Iodine Radioisotopes; D010472:Perchlorates; D000644:Quaternary Ammonium Compounds; D017942:Nitric Acid; D007455:Iodine; C027917:tetramethylammonium