电位滴定法检测茶叶水溶性灰分碱度

目的建立一种电位滴定法检测茶叶水溶性灰分碱度。方法选用不同品种的茶叶,按照国家标准方法 GB/T 8309-2013《茶水溶性灰分碱度测定》对样品进行炭化、灰化、加热、洗涤后,分别采用电位滴定法和国家标准方法进行测定,并对2种方法的测定结果进行比较。结果测定茶叶水溶性灰分碱度,电位滴定法测定空白样品标准偏差0.001%,样品标准偏差0.028%～0.031%;国家标准方法测定空白样品标准偏差0.003%,测定样品标准偏差0.044%～0.061%。电位滴定方法加标回收率为89.9%～92.6%,方法检出限0.003%。结论电位滴定法测定茶叶水溶性灰分碱度的准确性高、稳定性好、可操作性强,能排除更多干扰,可推广使用。

Determination of alkalinity of water-soluble ash content in tea by potentiometric titration

Objective To establish a method to detect the alkalinity of water-soluble ash in tea by potentiometric titration. Methods Different kinds of tea samples were selected, then carbonized, ashed, heated and washed according to the national standard method GB/T 8309-2013 Tea-Determination of alkalinity of water-soluble ash, and determined by the potentiometric titration method and the national standard method respectively. The results of the two methods were compared. Results The standard deviations of blank and sample was 0.001% and 0.028%~0.031% respectively by potentiometric titration method, and that was 0.003% and 0.044%~0.061% respectively by the national standard method. The standard recovery rates of potentiometric titration method were ranged from 89.9% to 92.6%, and the limit of detection was 0.003%. Conclusion The potentiometric titration method has the advantages of high accuracy, good stability and strong operability, which can eliminate more interference.in detecting the alkalinity of water-soluble ash of tea. It can be adopted widely.