HPLC法测定茶叶水提液中五种儿茶素和咖啡碱及其用于茶叶分类的研究

Simultaneous Determination of Five Catechins and Caffeine in Tea by HPLC and Differentiation of Teas by Cluster Analysis

建立高效液相色谱/二极管阵列检测器(HPLC/DAD)同时测定茶叶中(-)-没食子儿茶素(GC),(-)-表没食子儿茶素(EGC),(-)-表没食子儿茶素没食子酸酯(EGCG),(-)-表儿茶素(EC),(-)-表儿茶素没食子酸酯(ECG),咖啡碱(caffeine)6种组分的分析方法,并采用聚类分析探讨以这6种活性成分为指标对茶叶进行分类的方法。采用C18柱,甲醇和0.05%三氟乙酸水溶液为流动相,梯度洗脱,DAD双波长(210、278 nm)同时检测,采用标准物质保留时间和电喷雾飞行时间质谱(ESI TOF-MS)双重定性。结果表明,各组分的色谱峰均达到基线分离,在210 nm对(-)-没食子儿茶素(GC)定量,278 nm对其它组分定量准确。该法重复性好,灵敏度高,回收率高,已用于不同种类的33种实际茶叶样品的测定。以这6种活性成分的含量为指标,采用聚类分析法可对33个红茶、黑茶、绿茶、乌龙茶样本进行合理分类,并能反映茶叶品质的差异。

A method was developed for simultaneous determination of five catechins （ （ - ）-gallocatechin, （ - ）-epigallocatechin, （ - ）-epigalloeateehin-3-gallate, （ - ）-epicatechin, （ - ）-epicatechin- gallate） and caffeine by HPLC with diode array detection （DAD）. The tea extract was separated on a C18 column which was then eluted with methanol and 0. 05% trifuoroacetie acid solution in gradient elution mode. The chromatograms were simultaneously detected by DAD at λ210 nm for （ - ）-galloeateehin （GC） and at λ278 nm for the other components. Time of flight mass spectroscopy（ TOF -MS） was used for qualitative analysis of real tea sample, the results showed that five cateehins and caffeine were baseline separated, indicating that the six components could be determined accurately. The method has been used to determine the catechins and caffeine in 33 tea samples with satisfactory results. Cluster analysis has been used to classify 33 tea samples reasonably and to differentiate the qualities of the tea by using the concentrations of the six components as indices.