用柱前衍生CE-ECL法测定茶叶样品中茶氨酸的含量

Determination of Theanine Content in Tea Samples by Precolumn Derivatization CE-ECL Method

利用自制的交联壳聚糖修饰毛细管为分离毛细管,采用毛细管电泳-电致化学发光法(CE-ECL)对六种常见商品茶叶中茶氨酸含量进行测定。在最优实验条件下,茶氨酸衍生物在5 min之内达到基线分离。在5.0~200μM浓度范围内,茶氨酸衍生物的浓度与其电泳峰强度呈良好的线性关系(R^2=0.9952),检测限为2.8μM。在75μM浓度水平上,用茶氨酸纯品进行衍生反应并平行测定6次,其电泳峰高和迁移时间的相对标准偏差分别为2.49%和1.14%。此外,采用标准加入法对几种茶叶中的茶氨酸含量进行了实样测定,结果表明白茶、红茶、龙井茶、绿茶、铁观音茶和普洱茶中茶氨酸的测得值分别为1.53%、0.91%、0.61%、0.37%、0.28%和0.14%(以干茶样的质量比计算)。同时,采用白茶样品进行了加标回收实验,加标回收率为105.3%。该方法快速、简便,可适用于不同种类商品茶叶中茶氨酸含量的测定。

With the homemade cross-linking chitosan coating capillary as separation capillary, the content of theanine in six kinds of marketed tea samples was taken separation and determination by CE-ECL method, Under the optimal experimental conditions, the rapid separation of theanine derivative could be attained within 5 rain, The linear ranges was 5-200 μM for theanine, and its detection limit （S/N = 3） was 2.8 μM. The repeatability of this method was investigated by six consecutive injections of a standard derivative solution containing 75 taM theanine, and the RSD values of both migration time and ECL peak intensity were 1.14 % and 2.49 %, respectively. By using standard addition method, the content of theanine in the six original tea samples were successfully obtained, while the specific data of theanine content in the tea samples were 1.53 %, 0.91%, 0.61%, 0.37 %, 0.28 % and 0.14 % （by dry weight measure） for White tea, Black tea, Longiin tea, Green tea, Pu＇er tea and Tie guanyin tea, respectively. Meanwhile, the recoveries of theanine in the actual White tea samples were attainable 105.3 %. This method was much simple and rapid, and could be suitable to the different tea products analysis.