The mobile phase consisted of 0.1% aqueous formic acid (A) and 0.06% formic acid in methanol (B), using a gradient elution of 5%20% B at 010 min and 20% B at 1032 min. Absorption wavelength was selected at 210 nm. The column temperature was kept constant at 30 °C. The UV spectrum obtained for each peak, after subtraction of the corresponding UV base spectrum, was computer normalized and the plots were superimposed. Peaks were considered to be chromatographically pure when there was exact coincidence of their corresponding UV spectra.