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Trace Elements in Norwegian and Polish Tea Infusions: Determined by High-Resolution Inductively Coupled Plasma Mass Spectrometry (HR ICP-MS) and Ion Selective Electrode (ISE)
Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, Department of Chemistry.
2013 (English)MasteroppgaveStudent thesis
Abstract [en]

AbstractTea from the plant Camellia sinensis is the world’s most popular non-alcoholic beverage, next to water. Tea can be divided into six types, and the most popular teas are black tea, green tea and oolong. In this study infusions of 85 Norwegian and Polish tea samples were analysed to investigate the content of trace elements. 40 samples from Norwegian supermarkets, 30 from the local tea and coffee shop and 15 Polish samples were infused for 5 minutes with ultrapure boiling water (1 gram tea/100 mL). The fluoride content in the tea infusions was determined using an ion selective electrode (ISE), and the rest of the elements were determined by high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS). Tea is a rich source of essential elements as calcium (Ca), phosphorus (P), potassium (K), magnesium (Mg), manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn). The infusions also contain non essential elements as nickel (Ni),lead (Pb), fluoride (F) and aluminium (Al). The average concentrations in one cup of tea from the Norwegian market contains among other elements average concentrations of 0.6 mg Ca/L, 2.8 mg P/L, 37.1 mg K/L, 2.0 mg Mg/L, 5.9 µg Fe/L, 14.1 µg Cu/L, 26.4 µg Zn/L, 0.6 mg Mn/L, 9.9 µg Ni/L, 0.16 µg Pb/L, 0.5 µg Cr/L, 1.0 mg F/L and 1.1 mg Al/L. For the essential elements Ca, P, K, Mg, Fe, Cu and Zn the tea infusions will not contribute to attain the recommended dietary allowances (RDAs) in any extent, but for Mn where the AI are 2.3 mg/day (men) and 1.8 mg/day (women) a few cups of tea can exceed the given AI level. The amount of Pb in the infusions is sustainable lower than the provisional tolerable weekly intake (PTWI) of 25 µg/kg body weight. Drinking tea will therefore not contribute in any high extent to the PTWI.There were on the other hand obtained vast variations of F concentrations in different types of tea and tea contributes also in huge extent to AI of F - 3 mg/day (women), 4 mg/day (men) and from 0.5- 1 mg/day (0 -12 year olds). One cup of tea could easily exceed the AI, at least considering children drinking tea. The Al content in tea is high, and for heavy tea drinkers may tea be the largest single source of Al to contribute to the total weekly intake (TWI) of 1 mg/ kg body weight/ week.The study showed higher concentrations of elements in tea infusions made of tea bags than infusions made of loose tea. Suggesting that the elements in the crushed leaves in tea bags are more extractable than in the loose tea leaves. One other explanation is that the tea bags contain older tea leaves with lower quality and therefore older leaves with higher concentrations of e.g. Al. There was also seen a significant difference in the element composition in Norwegian and Polish infusion, with higher concentrations of elements in the Norwegian infusions.

Place, publisher, year, edition, pages
Institutt for kjemi , 2013. , 76 p.
URN: urn:nbn:no:ntnu:diva-21166Local ID: ntnudaim:8598OAI: diva2:631303
Available from: 2013-06-20 Created: 2013-06-20 Last updated: 2013-11-20Bibliographically approved

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