Isolation and purification of epirubicin from raw product by preparative chromatography on a silica column with aqueous-rich mobile phase

A novel chromatographic method has been developed for the preparative separation of epirubicin from raw product solution in overloaded elution mode using an analytical silica column with aqueous-rich mobile phase. The retention behavior of sample solutes was investigated in order to optimize the resolution by changing the mobile phase composition, flow-rate, and column temperature. It has been found that the high-purity silica exhibits typical reversed-phase behavior in a highly aqueous environment with little or organic modifier, and the nature of the organic modifier has little effect on its hydrophobic property. More significantly, the overloaded peak profiles of the solutes under such conditions were right-angled triangle with the rear of the peaks in coincidence, a typical overloading peak profile belonging to competitive Langmuir isotherm. The preparative separation was optimized by adjusting the sample size and detecting the sample at its low UV absorbance, and the positions of the cut points were determined by the detector response values. Even with an a value as small as 1.04, satisfactory preparative separations were observed by effectively utilized displacement effects and touching-band optimization. The recovery of epirubicin was 90% and the purity was more than 99% as measured by RPLC on a C-18 column. The added stepwise elution was a crucial procedure since it not only promoted the separation time but also regenerated the silica column to prolong its lifetime.