The following gradient was at 86% B at 0–10 min, 74% B after 32 min, 20% B for 35–38 min, and 86% B for 40–43 min. Flow rate was 1 mL/min, and column temperature was 40 °C. Detection was performed by scanning from 200 to 540 nm and the quantitative analysis was done at 280 nm.