Simultaneous analysis of theanine, chlorogenic acid, purine alkaloids and catechins in tea samples with the help of multi-dimension information of on-line high performance liquid chromatography/electrospray–mass spectrometry

A reverse phase high performance liquid chromatography (RP-HPLC) separation coupled with photo diode array detection (DAD) and electrospray ionization mass spectrometry (ESI–MS) detection was established for the analyzing of multiple bioactive compounds in tea and tea extracts. Theanine, chlorogenic acid, purine alkaloids and catechins were identified with authentic standard compounds and with MS-spectra. The content of theanine and catechins was measured by employing DAD and caffeine, chlorogenic acid, theobromine and theopylline by protonated molecular ion on selective ion recording (SIR) mode. The unity of LC/ESI–MS provides more qualitative and quantitative information comparing with general HPLC in the analysis of multi-components in tea, and complex extraction or sample pretreatment is unnecessary. The chromatogram acquired by using this method can be used as a bioactive components fingerprint for the quality control of tea and its extracts. With the help of multi-dimension information of HPLC–DAD–ESIMS, the compounds owning different chemical structure such as amino acid, catechins, etc. in tea and its extracts could be identified and determined in one run successfully.