Table 1. HPLC-UV double gradient elution scheme.

Time (min)	Flow rate (ml/min)	A (%)	B (%)
0.01	0.3	10	90
4	0.3	30	70
6	0.3	25	75
8	0.3	25	75
11	0.3	18	82
16	0.3	10	90
20	0.3	10	90

A, acetonitrile; B, 0.1% formic acid in water.