Rapid visualized characterization of phenolic taste compounds in tea extract by high-performance thin-layer chromatography coupled to desorption electrospray ionization mass spectrometry.

Phenolic compounds are the important taste source of tea infusion. In this paper, the phenolic compounds in tea extracts were separated by high-performance thin-layer chromatography (HPTLC), and then in-situ determined by desorption electrospray ionization mass spectrometry (DESI-MS). Total 44 phenolic compounds in tea extracts were accurately confirmed by NIST library as well as reference substances. The clustering results of heat-map can better reflect the differences of phenolic compounds in different categories and subcategories of teas. Besides, the contents of hydrolyzable tannins, including galloylglucose, digalloylglucose, trigalloyglucose and strictinin, were positively correlated with the grades of green tea. The method validation and quantification results of exemplified five phenolic compounds in teas were also obtained, and LODs, LOQs and recoveries were ranging between 1.5-15.9 μg/mL, 5.1-53.1 μg/mL, and 79%-117.6%, respectively. Moreover, HPTLC-DESI-MS can save tenfold analytical time compared to HPLC-MS. Therefore, HPTLC-DESI-MS was a rapid, efficient characterization method of phenolic compounds in tea extracts.