The Waters Synapt G2-S quadrupole time-of-flight mass spectrometer with an electrospray ionization (ESI) source (Milford, MA, USA) was coupled to an Acquity UPLC system (Waters). The chromatographic separation was performed on SeQuant® ZIC®-cHILIC HPLC (100 mm x 2.1 mm, 100 Å pore size, 3 µm) column. The column oven and autosampler temperatures were set at 40 o C and 10 o C respectively. Mobile phase A (MPA) consisted of acetonitrile:water (9:1) containing 5 mM ammonium acetate and acetonitrile:water (1:9) with 5 mM ammonium acetate was used for mobile phase B (MPB). The flow rate was 0.25 mL/min and injection volume was 5 µL. The gradient elution is shown in Table . The autosampler injection needle was washed with a weak needle wash consisting of acetonitrile:water (1:9, v/v) and strong needle wash consisting of acetonitrile:water (9:1, v/v).