Investigation on the effect on moisture content of freeze-dried powder of biological products

To study the causes of increasing moisture content in freeze dried powder of biological products after been laying a period by moisture control test, the tests for moisture content,vacuum weight loss on drying of dimethicone and rubber stopper of vial were performed. Average moisture content of a rubber stopper was 0.00224g after freeze-dried. The increasing moisture content of samples was due to the incompletely removal of the moisture of rubber stopper during sterilizing, drying and freeze-drying process.