title: Comparison of methods for iodine analysis in foods.
abstract: Spectrophotometric and ICP-MS methodology for iodine determination was compared. Samples were alkali dry-ashed, dissolved in water, and iodine assayed by spectrophotometry and by ICP-MS. Iodine content in the studied foods ranged from 3 to 1304μg/100g. There was no significant difference (p>0.05) between iodine values determined spectrophotometrically using an external calibration curve and values determined using a standard addition. Foods containing low iodine concentrations (4-25μg/100g) also showed no significant difference (p>0.05) between iodine concentrations determined spectrophotometrically and concentrations determined by ICP-MS. For food items with more than 25μg/100g, the spectrophotometric methods yielded markedly higher (p<0.05) concentrations than the standard ICP-MS method (relative positive bias 25-122%), especially in foods with high sodium and/or iron contents. A catalytic effect of sodium and iron on the Sandell and Kolthoff reaction, leading to false high values in the spectrophotometric determination of iodine was demonstrated. ICP-MS is recommended for iodine determination in foods.
authors.affiliation: Institute of Nutrition, Mahidol University, Putthamonthon 4 Rd., Salaya, Phutthamonthon, Nakhon Pathom 73170, Thailand. Electronic address: kunchit.jud@mahidol.ac.th.
authors.forename: K
authors.initials: K
authors.lastname: Judprasong
authors.affiliation: Bureau of Nutrition, Department of Health, Ministry of Public Health, Maung, Nonthaburi 11000, Thailand.
authors.forename: N
authors.initials: N
authors.lastname: Jongjaithet
authors.affiliation: Institute of Nutrition, Mahidol University, Putthamonthon 4 Rd., Salaya, Phutthamonthon, Nakhon Pathom 73170, Thailand.
authors.forename: V
authors.initials: V
authors.lastname: Chavasit
mesh_terms: D002138:Calibration; D005502:Food; D005504:Food Analysis / Q000379:methods*; D007455:Iodine / Q000032:analysis*; D007501:Iron / Q000032:analysis; D013058:Mass Spectrometry; D012964:Sodium / Q000032:analysis; D013053:Spectrophotometry
chemical_list: D007455:Iodine; D012964:Sodium; D007501:Iron
keywords: Food; ICP-MS; Iodine; Sandell and Kolthoff reaction