a b s t r a c t
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 1304 lg/100 g. 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
(4–25 lg/100 g) 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
25 lg/100 g, 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.
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