市售罐裝茶飲料中兒茶素類及咖啡因含量之分析   全文下載

Analysis of Catechins and Caffeine Contents in Commercial Tea Drinks

本文乃就市售數種不同廠牌及茶種之罐裝茶飲料，利用短管柱（12.5公分長）逆相（RP-18，0.45μm）高效液相層析法進行分析。利用合20%甲醇及2-3%醋酸之水溶液當作移動相，流速為每分鐘0.75ml的條件下進行分析，可在20分鐘內將四種主要的兒茶素類（包括EGC, EGCG, EC及ECG）及咖啡因完全分離，達到定量的目的。市售不同廠牌罐裝茶飲料中兒茶素類的含量有明顯差異（19-146ppm），紅茶類較低，綠茶類與烏龍茶類較高，但後兩者間並無顯著不同。值得注意的是，同一批產品，儲存期長者之兒茶素的含量有下降趨勢。就茶葉中兒茶素類物質之一般含量而言，市售茶飲料中此類兒茶素（特別是EGCG）之存在量，相對於高濃度的咖啡因（約在60至300ppm之間）顯然偏低。茶飲料在分析前進行氯仿（chloroform）處理，不會明顯影響兒茶素的測定，卻可除去高量咖啡因存在時可能造成的干擾。改變偵測波長為245nm可降低EGC檢出之可能誤差。另一方面，由數據顯示Vanillin法並不適合於罐裝茶飲料中兒茶素類物質之分析。 In this study, several commercial tea drinks of different manufacture and fermentation were analyzed by an isocratic HPLC for their catechins and caffeine contents. By using a short RP-18 column (4x125 mm, 0.45 μm), four major catechins (namely EGC, EGCG, EC and ECG) and caffeine were totally separated within 20 minutes at a flow rate of 0.75 ml/min, when water/MeOH/HOAc (77-78/20/2-3, V) was used as the mobile phase. Caffeine (60-300ppm) content was always higher than the concentration of total catechins (19-146 ppm). The catechin contents in samples decreased after prolonged storage. Changing the monitoring wavelength from 280 nm to 245 nm improved the detection accuracy of EGC; its molar extinction coefficient is higher at A245‧ Chloroform treatment of tea samples can also prevent the interference that results from the presence of relatively large amounts of caffeine. On the other hand, the vanillin method was proven to be unsuitable for the analysis of catechins in processed tea drinks."

In this study, several commercial tea drinks of different manufacture and fermentation were analyzed by an isocratic HPLC for their catechins and caffeine contents. By using a short RP-18 column (4x125 mm, 0.45 µm), four major catechins (namely EGC, EGCG, EC and ECG) and caffeine were totally separated within 20 minutes at a flow rate of 0.75 ml/min, when water/MeOH/HOAc (77-78/20/2-3, V) was used as the mobile phase. Caffeine (60-300ppm) content was always higher than the concentration of total catechins (19-146 ppm). The catechin contents in samples decreased after prolonged storage. Changing the monitoring wavelength from 280 nm to 245 nm improved the detection accuracy of EGC; its molar extinction coefficient is higher at A245• Chloroform treatment of tea samples can also prevent the interference that results from the presence of relatively large amounts of caffeine. On the other hand, the vanillin method was proven to be unsuitable for the analysis of catechins in processed tea drinks.