Therefore, different compositions of mobile phase (water with acetic acid from 0.1% to 1.0% as solvent A and acetonitrile, methanol or a mixture of both of them as solvent B) were investigated
and finally methanol/0.5% aqueous acetic acid (65/35, v/v)was selected as a preferred mobile phase due to its better separation efficiency, shorter analysis time (-3.3 min) and lower toxicity.