Separation and identification of twelve catechins in tea using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry.

A method has been developed for the direct microscale determination of 12 catechins in green and black tea infusions. The method is based on liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (LC/APCI-MS). Standard catechin mixtures and tea infusions were analyzed by LC/APCI-MS with detection of protonated molecular ions and characteristic fragment ions for each compound. The identities of eight major catechins and caffeine in tea were established based on LC retention times and simultaneously recorded mass spectra. In addition, monitoring of the catechin-specific retro Diels-Alder fragment ion at m/z 139 throughout the chromatogram provided a unique fingerprint for catechin content in the samples that led to the identification of four minor chemically modified catechin derivatives in the infusions. This report is the first to describe the comprehensive determination of all 12 reported catechins in a single analysis. The utility of LC/APCI-MS for providing routine separation and identification of catechins at femtomole to low-picomole levels without extraction or sample pretreatment, and its potential as a standard analytical tool for the determination of polyphenols in natural products and biological fluids, are discussed.