Two microlitres were injected on an ACQUITY UPLC BEH C18
1.7 mm column (2.1 mm50 mm) (Waters) at 25C. The mobile phase
was maintained at a flow rate of 388 ml/min using binary solvent system
of 0.1% formic acid in water (A) and methanol (B). The elution gradient
started at 10% B (0–1 min), linearly increased to 50% B (1–8 min), held
at 100% B (8–9 min), decreased to 10% B (9–10 min), and held at 10%
B (10–20 min).