A comparison of vials with ampoules for the storage of biological reference materials

Lyophilization is a key strategy in the stabilization of biological materials. Protection of the lyophilized material from an oxidizing atmosphere is essential if stability is to be maintained under long term storage. Vials of lyophilized albumin closed by two methods and ampoules of albumin have been examined for moisture and oxygen ingress after storage both under conditions of stress for two months and under thermally accelerated conditions for one year. The results show that the gas and moisture contents of ampoules do not detectably change even under conditions of stress, in contrast to vials for which this study shows clearly detectable moisture ingress and suggests some oxygen ingress. This is consistent with the results of other studies. Thus, although vials may be satisfactory under constrained conditions of temperature and storage for limited periods of time, and are presently used satisfactorily for some working standards, it would be prudent to continue to use ampoules for storage of international reference materials which are intended for indefinite storage and for which stability is an essential requirement.