核磁共振法无损伤测定五峰绿茶中咖啡因含量

Non-damage Determination of Caffeine Content in Wufeng Green Tea by NMR Method

为了建立核磁共振法无损伤快速测定茶叶中咖啡因含量,采用微型实验装置,以恒压滴液漏斗连续萃取,并改进升华装置,从茶叶中提取咖啡因作为标样。通过核磁共振法测定一系列梯度浓度的咖啡因标样核磁氢谱,利用谱图积分功能,对8.05（s,1H）质子峰进行积分,建立咖啡因含量标准曲线方程y=100.428 57x＋0.125 39。咖啡因在0.125 4-2.234 3 mg时,核磁氢谱积分面积（y）与咖啡因含量（x）呈良好的线性关系（r=0.999 9）,加标回收率为98.8%-101.1%,相对标准偏差RSD为0.36%。将不同等级的五峰绿茶,利用甲醇浸提冷冻干燥技术,分别测试样品的核磁氢谱,通过标准曲线求解咖啡因含量,以期建立快速准确、无损伤,预处理简便的茶叶中咖啡因含量的检测方法。

In order to establish nuclear magnetic resonance method for no damage and rapid determination of caffeine content in Tea,the miniature experimental device was adopted to extract of caffeine from tea as the standard sample,with the constant pressure drop funnel continuous extraction and improved sublimation apparatus. Determined through a series of graded concentrations of caffeine ^1H NMR spectra,using the integral function for 8. 05（ s,1H） proton peak,the standard curve of caffeine content of the equation y = 100. 428 57 x ＋ 0. 125 39 is established. When the caffeine in0. 125 4 - 2. 234 3 mg,^1H NMR integral area（ y） and caffeine（ x） showed a good linear relationship（ R = 0. 999 9）,and the recovery rate was 98. 8% - 101. 1%,the relative standard deviation is 0. 36% for RSD. The caffeine content in different grades of Wufeng Green Tea are obtained through the standard curve by the methanol extraction freeze-drying technique and ^1H NMR spectra of each sample,in order to build fast and accurate,non-damage,simple pretreatment methods of detection caffeine＇s content.