Objective To explore the stability of fluoride ion selective electrode method to detect fluorine content in brick tea, and provide theoretical data for its calibration. Methods Samples were extracted by boiling water, using TISAB buffer solution to eliminate the effect of interfering ions and acidity, and then measured by fluoride ion selective electrode. Results The factors had an obvious influence on the content of fluorine in brick tea, such as the buffer ionic strength, sample consumption, electrode, stirring speed, and filtra-tion condition. The detection of fluorine content in brick tea by using 120 g/L (TISAB-2) sodium citrate buffer solution were more accurate, and there was no significant difference in fluorine content between 120 g/L (TISAB-2) and 110 g/L (TISAB-GB) sodium citrate buffer solution. The fluorine content in 0.25 g samples reached the high value of 490.73±6.36 mg/kg, and this fluorine content was more accurate. The determination results showed that the new electrode was more stable than that by older electrode, the medium and high stir-ring speed were more stable and reliable than low stirring speed, and the qualitative filtration was much better than no filtration and quantitative filtration. Conclusion Under the optimum conditions, this method is accu-rate and stable, and it is suitable for the determination of fluorine content in brick tea.% 目的探讨氟离子选择电极法测定砖茶氟含量的稳定性,为该方法的校准提供理论数据。方法样品经沸水提取、缓冲溶液消除离子及酸度的干扰后,采用氟离子选择电极法测定砖茶试样中氟含量。结果缓冲溶液(TISAB)离子强度、试样用量、电极、搅拌速度、过滤条件等实验因素对样品氟含量测定结果影响极显著,其中以含柠檬酸钠120 g/L(TISAB-2)的缓冲液测定结果较准确,且与国标法(TISAB-GB)测定结果差异不显著；试样用量为0.25 g时,样品中氟含量值较高,为490.73±6.36 mg/kg,测定结果准确；新电极较旧电极测定结果稳定性好；中、高转速较低搅拌速度测定结果稳定可靠；定性过滤条件下的测定结果优于不过滤和定量过滤。结论在优化的实验条件下,氟离子选择电极法测定样品中氟含量,结果较为准确,稳定可靠,适用于砖茶中氟含量的测定。
展开▼
