Table 1.

The gradient elution procedure of HPLC.

Time (min)	Mobile phase
0–2.0	90%A*
2.0–3.0	90%A-80%A
3.0–5.0	80%A-74%A
5.0-7.0	74%A
7.0–10.5	74%A-40%A
10.5–13.5	40%A
13.5–14.5	40%A-5%A
14.5–17.0	5%A
17.0–18.0	5%A-90%A
18.0–20.0	90%A

^*The mobile phase consists of 0.5 mmol/L ammonium acetate solution containing 0.1% formic acid (A) and methanol (B).