Separation and purification of two isomorphic steroids by a novel extractive drowning out crystallization

A novel extraction drowning out crystallization technology was brought forward for separation and purification of two isomorphic steroid pharmaceutical intermediates. In this process, extraction and crystallization are conducted in the same crystallizer simultaneously. The two immiscible (partial miscible) liquid phases were achieved by adding water into the toluene–DMF system. The role played by water is both as an antisolvent for a crystallization and a trigger to generate two immiscible phases for extraction. The advantage of this method is that two relative pure product can be achieved in a crystallization process. The experimental result shows a good prospect of this method for industrial separation of the studied two isomorphic steroids.