title: [Determination of catechins and caffeine in tea and tea beverages by high-performance liquid chromatography].
abstract: OBJECTIVE
  A high-performance liquid chromatography method was developed for the determination of total tea catechin and caffeine.
  
  
  METHODS
  The catechins needed to be determined are: (-)-catechin, (-)-epigallocatechin, (-)-epigallocatechin gallate, (-)-epicatechin, (-)-epicatechin gallate, (-)-gallocatechin, (-)-gallocatechin gallate, (-)-catechin gallate and caffeine. The catechins in the tea was extracted with water:ethanol (3:7) by sonication for 20 min. After the extraction solution was centrifuged, it was analyzed by HPLC. The column used was a CAPCELL PAK C18 MG (4.6mm I.D. x 150mm) and gradient elution at constant column temperature with 30 degrees C under UV detector with 210nm. Mobile phase A was 0.1% H3PO4 in water, mobile phase B was 0.1% H3PO4 in methanol with the flow rate 1ml/min.
  
  
  RESULTS
  The results showed that the concentration of the catechins and caffeine and their peak areas achieved good linear relation, r > 0.999. The recoveries were between 61.7%-117.3%. RSD was below 10%. With this method, some tea samples were determined, the results were favorable.
  
  
  CONCLUSIONS
  The method can be applied for determination of catechin and caffeine in tea and tea beverages.
authors.affiliation: National Institute for Nutrition and Food Safety, Chinese Center for Diseases Control and Prevention, Beijing 100050, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Ling
authors.forename: Yun-feng
authors.initials: YF
authors.lastname: Zhao
authors.forename: Zhi-jun
authors.initials: ZJ
authors.lastname: Li
authors.forename: Gong
authors.initials: G
authors.lastname: Zhang
authors.forename: Yongning
authors.initials: Y
authors.lastname: Wu
mesh_terms: D002110:Caffeine / Q000032:analysis* / Q000302:isolation & purification; D028241:Camellia sinensis / Q000737:chemistry*; D002392:Catechin / Q000032:analysis* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D012680:Sensitivity and Specificity; D013662:Tea / Q000737:chemistry*
chemical_list: D013662:Tea; D002110:Caffeine; D002392:Catechin