Combination of ICP-MS with chemometrics analysis to identify Iodine and Selenium contents in consumed Portuguese foods

Selenium and iodine are micronutrients essential for thyroid hormone synthesis and function. There is also some evidence that low plasma selenium and iodine levels increase the risk of autoimmune thyroid diseases. Plasma levels of these oligoelements are related with dietary intake. Since foods are their main natural sources we investigated iodine and selenium content in foods as consumed collected in Portuguese TDS pilot study as representative of diet in the country. Samples (n=492) were collected according to sampling plan from local markets and analyzed as pooled (n=41) of twelve samples each. The iodine and selenium contents were determined using inductively coupled plasma-mass spectrometry after alkaline (iodine) or acid (selenium) digestion assisted by microwave. To guarantee the accuracy of the laboratory results matrix matching reference materials and successfully participation in proficiency test schemes were chosen as metrological parameters. The analytical results were expressed by the average of three replicates. Cluster analysis and Spearman correlation were applied to evaluate the statistical significance of analytical data. Selenium content ranged from 109±10.85 µg/100g (fresh tuna) to 1.82±0.16 µg/100g (milk with cereals). Iodine values were found from 157±5.8 µg/100g (cockles and clams) to 0.27±0.014 µg/100g (lupine). Cluster analysis classified samples into four main groups on the basis of the iodine and selenium content. Spearman positive correlation (p≤ 0.05) was achieved between iodine and selenium contents. Application of chemometric methods to analytical data is useful to group food samples when iodine/selenium ratio is necessary to suppress iodine deficiency through dietary intake.

This work was undertaken within Total Diet Study Exposure (www.tds-exposure.eu), which is funded by the European Commission (Grant Agreement 289108)

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