Novel process for refining cefmetazole sodium

A process for refining Cefmetazole sodium, characterized in that, the process comprises the steps of:

• 1) dissolving Cefmetazole sodium material in water, adding ethyl acetate, cyclohexane, or a mixture of ethyl acetate and cyclohexane, and extracting for several times with the volume of the organic solvent preferably less than half of the volume of the aqueous solution each time, followed by separating the organic phase, to provide an aqueous phase containing Cefmetazole sodium;
• 2) treating by adding an alkoxide of alkali metal or alkaline earth metal into the above aqueous phase under heating, preferably at a temperature of 30-100° C., for a time range from several minutes to several hours, preferably from 30 minutes to 5 hours, followed by cooling down and filtrating the precipitate, to provide an aqueous filtrate;
• and
• 3) concentrating the Cefmetazole sodium aqueous solution provided in step 2) at elevated temperature, such as at 30-80° C., and recrystallizing by adding ethanol with a water-ethanol volume ratio of 4:6 or adding acetone with a water-acetone volume ratio of 5:5 under slowly cooling-down conditions until the temperature reaches between room temperature and −5° C., followed by centrifuging and washing the resultant crystals, to provide a thirdly purified Cefmetazole sodium after drying.