Analytical Problems with the Evaluation of Human Exposure to Fluorides from Tea Products

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 AS9-HC 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.

Risk Assessment of Fluoride Intake from Tea in the Republic of Ireland and its Implications for Public Health and Water Fluoridation

“…However, the possible interference of aluminium (Al) with fluoride measurement using ISE procedures was not examined in any of these studies. Our review of literature found that high Al concentrations exceeding 2.5 mg/L have been observed to result in under-representation of fluoride levels in tea infusions when measured by ISE method [ 159 , 160 ]. During the course of our study the Al content was measured using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) in a subsample of six tea infusions and one sample of drinking water by a third party laboratory.…”

Black Tea Source, Production, and Consumption: Assessment of Health Risks of Fluoride Intake in New Zealand

“…Bishnu et al (2009) reported that CPF pesticide residues have been found in tea at concentrations that may pose health hazards to the consumers [ 311 ]. High aluminium concentrations in tea infusions have also been found to result in underrepresentation of F levels in tea infusions when measured by ISE method [ 312 , 313 ]. However, it should be noted that no funding was provided to undertake this study and the aim of the study was to solely measure the ionic F levels in tea.…”

Determination of common inorganic anions in tea samples by ion chromatography

“…Bromide ions were not detected in any of the tea samples examined under the conditions used. Fluoride ions were not quantifi ed due to possible interferences originating from small organic acids, which can occur in tea products (JANISZEWSKA & BALCERZAK, 2013). Statistical analysis (t-test) has shown that the differences in the results obtained for the determined anions in various tea categories (sticks and bags, Assam and Ceylon, India and Sri Lanka) are not signifi cant (the calculated t-values < table values).…”