title: Rapid tea catechins and caffeine determination by HPLC using microwave-assisted extraction and silica monolithic column.
abstract: A rapid reversed-phase high performance liquid chromatographic method using a monolithic column for the determination of eight catechin monomers and caffeine was developed. Using a mobile phase of water:acetonitrile:methanol (83:6:11) at a flow rate of 1.4 mL min(-1), the catechins and caffeine were isocratically separated in about 7 min. The limits of detection and quantification were in the range of 0.11-0.29 and 0.33-0.87 mg L(-1), respectively. Satisfactory recoveries were obtained (94.2-105.2 ± 1.8%) for all samples when spiked at three concentrations (5, 40 and 70 mg L(-1)). In combination with microwave-assisted extraction (MAE), the method was applied to the determination of the catechins and caffeine in eleven tea samples (6 green, 3 black and 2 oolong teas). Relatively high levels of caffeine were found in black tea, but higher levels of the catechins, especially epigallocatechin gallate (EGCG) were found in green teas.
authors.affiliation: School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia. Electronic address: afidah@usm.my.
authors.forename: A A
authors.initials: AA
authors.lastname: Rahim
authors.forename: S
authors.initials: S
authors.lastname: Nofrizal
authors.forename: Bahruddin
authors.initials: B
authors.lastname: Saad
mesh_terms: D002110:Caffeine / Q000032:analysis / Q000302:isolation & purification*; D028241:Camellia sinensis / Q000737:chemistry*; D002392:Catechin / Q000032:analysis / Q000302:isolation & purification*; D005591:Chemical Fractionation / Q000295:instrumentation / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods; D008872:Microwaves; D010936:Plant Extracts / Q000032:analysis / Q000302:isolation & purification*
chemical_list: D010936:Plant Extracts; D002110:Caffeine; D002392:Catechin
keywords: Black tea; Catechin; Green tea; High performance liquid chromatography; Monolithic column; Oolong tea