Determination of Fluoride Content in Tea Infusion by Using Fluoride Ion-Selective Electrode

The fluoride content was analyzed in 43 tea infusion. The analyzed samples were the mints (family Lamiaceae), the mint (Mentha piperita) and lemon balm (Mellissa officinalis), green tea (Camellia sinensis) and pomegranate (Punica granatum) in tea bags, bottles and bulk purchased in local supermarkets and marketplaces in Split, Croatia, were determined. Potentiometric determination by using fluoride ion-selective electrode was applied in this work. Average F(-)concentration in all tested samples was 0.116 +/- 0.211 mg L-1. In order to get a better insight into the fluoride content in different plant samples, a One-Way ANOVA program R was used for statistical data analysis. Concentration of F- follows log-normal distribution with parameters distribution of average concentration value of 3.77 mg L-1 and variance 3.00 mg(2) L-2. F- concentration was higher (P < 0.001) in infusions of green tea (0.393 +/- 0.23 mg L-1) than in infusions of mint (0.011 +/- 0.004 mg L-1) and pomegranate (0.008 +/- 0.002 mg L-1) tea. On the other hand, F- concentrations (P < 0.001) were lower in bulk samples (0.008 +/- 0.003 mg L-1) than in tea bags ones (0.164 +/- 0.259 mg L-1) and tea beverages (0.161 +/- 0.116 mg L-1). F- content was statistically different among same plant samples in correlation of samples packing. For green tea samples (P < 0.001) F- concentration was higher in tea bags (0.558 +/- 0.12 mg L-1) than in bottled green tea beverage (0.161 +/- 0.12 mg L-1). We have got same situation for pomegranate tea samples, in tea bags (0.00921 +/- 0.002 mg L-1) and bulk ones (0.00713 +/- 0.002 mg L-1) respectively. For mint tea samples we did not find correlation between sample packing and F- concentration.