title: [Theanine, EGCG and caffeine determinated by HPLC].
abstract: OBJECTIVE
  A high-performance liquid chromatography (HPLC) method was developed for the determination of theanine in puer tea without derivatization and HPLC for EGCG and caffeine with ingredient elution system was put forward.
  
  
  METHODS
  The theanine in the tea was extracted with water. The EGCG and caffeine was extracted with water: ethanol (3:7) by ultrasonic oscillation. After centrifugation, the extract was analyzed by HPLC-PDAD with a C18column and at the flow rate 1 ml/min. The theanine was determinated with 5 mmol/L SDS-acetonitrile mobile phase system (72:28), and both EGCG and caffeine with 0.05 mmol/L KH2PO4-methonal mobile phase system (80:20).
  
  
  RESULTS
  The calibration of three ingredients was in good linearity. The recovery range is 85%-110%. The RSD is less than 10%.
  
  
  CONCLUSIONS
  The method is accurate and stable.
authors.affiliation: Department of Chemical and Bacterial Detection, School of Public Health, Shandong University, Ji'nan 250012, China. diaofeiyan321@163.com
authors.forename: Feiyan
authors.initials: F
authors.lastname: Diao
authors.forename: Fengming
authors.initials: F
authors.lastname: Dong
authors.forename: Qiuli
authors.initials: Q
authors.lastname: Wang
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.forename: Dongmei
authors.initials: D
authors.lastname: Guo
authors.forename: Xi
authors.initials: X
authors.lastname: Cui
mesh_terms: D002110:Caffeine / Q000032:analysis*; D002392:Catechin / Q000031:analogs & derivatives* / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D005971:Glutamates / Q000032:analysis*; D012680:Sensitivity and Specificity; D013662:Tea / Q000737:chemistry*
chemical_list: D005971:Glutamates; D013662:Tea; D002110:Caffeine; C026166:theanine; D002392:Catechin; C045651:epigallocatechin gallate