The international reference preparation of hygromycin B.

The Central Veterinary Laboratory, Weybridge, England, was requested by the WHO Expert Committee on Biological Standardization to obtain suitable material for an international reference preparation of hygromycin B and to arrange a collaborative assay. A batch of 150 g of a highly purified hygromycin B was assayed in eleven laboratories in nine countries against the hygromycin B standard of a commercial manufacturer. On the basis of the results obtained, the material has been established as the International Reference Preparation of Hygromycin B and the International Unit for Hygromycin B has been defined as the activity contained in 0.0008928 mg of the International Reference Preparation of Hygromycin B.