Experimental Conditions Separations were performed by using an Agilent 1100 HPLC system equipped with binary pump and solvent degasser, autosampler, column compartment and diode array detector. The output of the diode array detector was introduced into the APCI source of the JEOL AccuTOF™ time-of-flight LC/MS system, operated at a resolving power of 6,000 (FWHM) in positive-ion mode with an orifice 1 potential of 28 V. Tea samples included a high-quality green tea, a common brand of black tea, and powdered teas. The HPLC separation made use of a Phenomenex 2mm x 150mm LUNA 5μ C18(2) column and guard column 2 operated at 35 deg. C with a solvent flow rate of 0.25 ml/min. Solvent A was 0.1% TFA in water, and sovent B was acetonitrile. The solvent composition was varied from 0% B to 30% B in 30 minutes and held at 30% B until 47 minutes. The autosampler was programmed for 10 μl injections of the tea samples.