探讨了低pH沉淀法检测茶叶中结合咖啡碱的可行性和优势,旨在为更精确地定量茶叶中的咖啡碱提供理论参考。研究以绿茶水提物、红茶水提物和普洱茶（熟茶）水提物为材料,应用低pH沉淀法检测了试样中的结合咖啡碱含量,并结合氯仿萃取法对检测结果进行了验证。结果表明,低pH沉淀法能够准确、简便地检测茶叶中的结合咖啡碱,其中普洱茶（熟茶）水提物中的结合咖啡碱含量最高（含2.59%）,而绿茶和红茶水提物中只有极少量的咖啡碱为结合态（含量分别为0.04%和0.07%）。
The feasibility and superiority in the determination of conjugated caffeine in tea by the method of low-pH precipitation was investigated in order to provide some theories for the determination of caffeine content in tea accurately. The aqueous extract of green tea, black tea and fermented Pu-erh tea were selected as test samples. The content of conjugated caffeine of the tea samples was determined by the method of low-pH precipitation. Meanwhile, the results of conjugated caffeine content were verified by the method of chloroform-extraction. The results showed as follows: Low-pH precipitation method is suitable for the determination of conjugated caffeine in tea. The content of conjugated caffeine in fermented Pu-erh tea is the highest (2.59%) among the three tea samples. However, the contents of conjugated caffeine in the green tea and black tea were relatively low (0.04% and 0.07% respectively).
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