with a slight modification: 5 lL tea solution pre-filtered with a
0.45 lmpolyethersulfone filter was separated with a 25-min linear
gradient from 80% to 55% mobile phase B (HPLC grade methanol)
and 20% to 45% mobile phase B (0.2% formic acid, pH 2.5) at
1 mL min1 on an Eclipse XDB-C18 column (4.6 250 mm, 5 lm,
Agilent) at 40 C.