*2.2. Sample Cleanup*

The sample cleanup was carried out using reversed phase C18 solid phase extraction (SPE) cartridges (Discovery DSCC18 500 mg/5 mL, Supelco, Bellefonte, PA, USA), as described previously [21]. The SPE cartridges were conditioned using 5 mL of methanol and water, respectively. The cartridges were loaded with 50 mL of the filtered infusion, washed with 6 mL of water and then dried with a vacuum manifold for 10 min. The elution of the PAs for all the tea samples was done by adding 5 mL of methanol. The elution step was repeated. The eluates were combined, dried under a gentle nitrogen stream in a warmed water bath (50 ◦C, TurboVap, Biotage, Uppsala, Sweden) and reconstituted in 1 mL of methanol/water (5/95, *v*/*v*). The extracts were transferred into filter columns (Nylon, 0.2 μm, VWR, Darmstadt, Germany) and centrifuged at 13,000× *g* for 2 min at room temperature.
