中文摘要：

采用超声萃取-紫外分光光度法测定五种不同的茶叶中咖啡因的含量，结果表明：最佳超声提取条件：超声功率150 W，温度60℃，时间30 min；5种不同茶叶咖啡因含量顺序为：粗老绿茶﹥普洱﹥金骏眉﹥信阳毛尖﹥铁观音。紫外分光光度计法显示：水溶剂咖啡因的最大吸收波长为273 nm，线性回归方程为：A=0.04855C-0.02854，r为0.9992，浓度在0.00～25.00μg/mL，线性关系良好，平均回收率为96.42%，RSD﹤2.0%。该方法简便快速，准确，可用于茶叶中咖啡因含量测定。

英文摘要：

By ultrasonic extraction and UV spectrophotometry detection the caffeine contents in five different types of tea were detected. The results showed the optimum ultrasonic extraction conditions： power 150 W, temperature 60℃, time of 30 min;the contentions of caffeine in five different tea are coarse old green tea﹥Pu ＆#39;er tea﹥Jinjunmei﹥Xingyang maojian﹥Tie Guanyin. The max absorbance of caffeine was detected by ultraviolet spectrophotometry at wavelength 273 nm.The relationship of the absorbance （A） and the concentration （C） was linear from 0.00 to 25.00μg/mL （r=0.999 2）, The linear equation was A=0.048 55C-0.028 54.The average recovery was 95.46%,the relative standard deviations were less than 2.0%.This method can he used for the determination of caffeine in tea because of its its simple ,rapid and accurate characteristics.