Sterility testing of insulin preparations

Abstract

The appearance of precipitates and opalescent components hinders testing for the sterility of insulin suspensions by seeding in cultural media. The sampling procedure is improved by dissolving preparations in 0.2% aqueous ascorbic acid solution, which eliminates opalescence and precipitation and facilitates the reading and interpretation of the test results as the test solutions become transparent. This method is suitable with both direct inoculation and membrane filtration. The insulin solution in 0.2% ascorbic acid does not exhibit antimicrobial activity, which makes expedient testing with the more economical direct inoculation.