Analytical Problems with the Evaluation of Human Exposure to Fluorides from Tea Products
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Analytical Problems with the Evaluation of Human Exposure to Fluorides from Tea Products Jolanta Janiszewska & Maria Balcerzak
Received: 5 July 2012 / Accepted: 14 September 2012 # The Author(s) 2012. This article is published with open access at Springerlink.com
Abstract Tea (Camellia sinensis) is a plant exhibiting high tendency for accumulation of fluorides. Up to 98 % of fluorides are accumulated in the leaves used for the preparation of widely consumed tea infusions. Fluorides from tea leaves are released into infusions, which make the second after drinking waters important source of fluorine for humans. A narrow margin between acceptable fluoride concentration and health risk requires a reliable examination of a large variety of tea products for fluoride contents. Large differences between the published results obtained by the use of different analytical techniques have stimulated studies on possibilities and limitations of different analytical procedures used for fluoride quantification in tea infusions. The applicability of ion selective electrode (ISE) and ion chromatographic (IC) methods to the determination of fluorides in the presence of aluminium, the element highly accumulated by tea trees affecting the amount of free fluoride ions occurring in tea infusions, was examined. The efficiency of different total ionic strength adjusting buffer (MES with citrates or tartrates and citrate) for the elimination of aluminium interference with fluoride detection by ISE method was compared. The applicability of three different chromatographic columns, Metrosep A Supp 4 and Metrosep A Supp 5 (both from Metrohm) and IonPac AS9HC from Dionex, to the isolation of free fluoride signals from the signals of interfering species, including acetates and formates, which can occur in tea samples, were examined. The contents of fluoride in various tea commercial products evaluated by ISE and IC methods applied are compared. J. Janiszewska : M. Balcerzak (*) Department of Analytical Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland e-mail: [email protected]
Keywords Tea . Fluoride . Aluminium . ISE method . Ion chromatography
Introduction Fluoride, a monovalent F− anion, is a reduced form of fluorine. Fluoride makes the predominant form of fluorine, one of the most chemically and physiologically active elements occurring in nature. Fluorine exhibits both beneficial and toxic effects to human body. Moderate levels of the element are beneficial for preventing dental caries and development of strong bones. A correlation between the rates of dental caries and fluoride concentrations in consumed drinking waters has been known since 1940s (Hardisson et al. 2003). Fluorides can improve bone mineralisation by substitution of hydroxyl groups in hydroxyapatite, Ca10(PO4)6(OH)2 involved in building of skeletal bone, generating fluoroapatite, Ca10(PO4)6OHF and Ca10 (PO4)6F2, of reduced crystal volume, increased structural stability and decreased mineral solubility (Ozsvath 2009). This can result in the r
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