Abstract: The influence of sample pretreatment methods including boiling water extraction (BWE),acidic solution extraction (ASE) and alkalizing and burning to ash(ABA) on fluorine content in tea and tea polysaccharides was investigated. The results showed that the fluorine contents of tea and tea polysaccharide pretreated with ABA were much higher than that of BWE and ASE method (P<0.01). The fluorine content of tea pretreated with BWE was significantly higher than ASE (P<0.05, P<0.01). The further test on precision and recovery of ABA and fluoride ion selective electrode method was investigated. Results showed that the recovery of fluorine in tea and tea polysaccharide were 91.07%-94.40% and 83.04%-90.32%, respectively, with RSD of 1.44%-2.54% for tea and 0.68%-1.03% for tea polysaccharide, which indicated the result of fluorine determination by this method could represent the real fluorine content in tea and tea polysaccharide with accuracy, reliability and stability. It was also suggested that the ABA and fluoride ion selective electrode method could be more suitable for determination of total fluorine in tea and tea extracts.

Key words: tea, tea polysaccharide, fluorine content, pretreatment, fluoride ion selective electrode