Separationswere carried out by means of a C18
BlueOrchid column (50 × 2 mm; 1.8 μm particle size; Knauer, Berlin,
Germany). The analytical mass spectrometric conditionswere optimized
by infusion of pure standards of 5-caffeoylquinic acid and caffeine. The
mobile phase, pumped at a flow rate of 0.3 mL/min, was acetonitrile in
0.1% aqueous formic acid and acidified water (0.1% formic acid) for all
the applied chromatographic separations. The gradient was a 9-minute
linear gradient of 3% to 20% acetonitrile in 0.1% aqueous formic acid.