Aluminium in tea: SEC-ICP-MS speciation studies of infusions and simulated gastrointestinal digests |
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Authors: | Linda M.W. Owen Helen M. Crews Robert C. Massey |
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Affiliation: | 1. Medical Research Council, Dunn Nutrition Unit, Milton Road, Cambridge CB4 1XJ;2. Ministry of Agriculture, Fisheries and Food, Food Science Laboratory, Food Safety Directorate, Norwich Research Park, Colney, Norwich NR4 7UQ, UK |
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Abstract: | AbstractThe speciation of aluminium in tea infusions and in vitro gastrointestinal digests of tea infusions has been investigated using size exclusion chromatography coupled to inductively coupled plasma mass spectrometry (SEC-ICP-MS). At pH 2.5, following simulated gastric treatment, Al from tea eluted at a similar retention volume to that obtained for an aqueous Al standard. At pH 5.5, an aqueous Al standard was eluted from an SEC column in Tris buffer (Al recovery ≈ 100%) only in the presence of a complexing agent (NaF), and at a retention volume corresponding to a molecular mass greater than that expected for an ionic species. Aluminium associated with a tea infusion eluted in two fractions: a higher molecular weight fraction corresponding to Al strongly bound to ligands in the tea, and a lower molecular weight fraction probably comprised of labile Al eluting as Al-F complexes. Simulated gastrointestinal digestion produced three Al-bearing fractions, of which the two at higher molecular mass represented ligand-bound Al. The molarity of the Tris buffer strongly influenced the retention volume of the Al fractions, particularly for the ligand-bound Al. After simulated gastrointestinal digestion, the soluble labile fraction (15% of the Al from the tea infusion) was considered to be potentially available for absorption. The actual proportion of the fraction that might be absorbed would depend upon a number of physiological and nutritional factors. |
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Keywords: | Size exclusion chromatography inductively coupled plasma mass spectrometry aluminium speciation tea infusion in vitro gastrointestinal digestion |
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