of Waters Acquity™ Binary Solvent Manager (two pumps), Sample Manager
(Autosampler) and PDA detector, managed with Waters Empower®
chromatography software version 3.0. LC separation was achieved on Acquity
UPLC® BEH C18 column (50 × 2.1 mm, 1.7 µm)
protected with VanGuard™ pre-column (5 × 2.1 mm, 1.7 µm)
from Waters Inc, Milford, MA, USA. The LC setting was as follows: Mobile phase
solvents were 25mM NH4AC 0.1% HOAC (A) and acetonitrile (B). The flow
rate was 0.6 mL/min. The gradient program consisted of 5%B (0–0.5min),
5–50%B (0.5–3.00min), 50–90%B (3.00–3.01min), 90%B
(3.01–3.50min), 90–5%B (3.50–3.51min), and 5%B
(3.51–4.00min). The column was heated at 40±5°C and
autosampler was cooled to 4±5 °C. The PDA detector was set at
261nm with a sampling rate of 40 points/sec. Injection volume was 5 µL.
The weak and strong needle wash solvents were 40% and 100% acetonitrile,
respectively. The seal wash solvent was 20% methanol.