Twin-column recycling chromatography with step solvent gradient and heart-cut technique for separation and purification of trace drug impurities.

This study presents a twin-column recycling chromatography method with a step solvent gradient, emphasizing the heart-cut technique to address co-elution challenges in trace impurity separation. By selectively diverting undesired components to waste and retaining the target fraction, the heart-cut method enhances resolution and purification efficiency. Experimental validation using crude Pulsatilla chinensis extract achieved the target trace compound purity of 99.9 %. This approach could reduce solvent usage and processing time, offering an efficient framework for isolating trace impurities in complex drug matrices.