Comparison of the effectiveness of various deaeration techniques

Abstract

Many methods have been described for the deaeration of dissolution media, as required by the USP as well as worldwide regulatory agencies. The USP General Chapter Dissolution <711> suggests heated vacuum filtration as one method of deaeration. This method of deaeration,when performed in our laboratories with 1L of water produced media with 2.8 mg/L dissolved oxygen remaining. Helium sparging achieved lower levels of dissolved oxygen. Helium sparging produced media deaerated to the same level as the USP vacuum filtration technique if the media was sparged at a flow rate of 40 mL/s for approximately 0.5 minutes per liter of media container volume. This recommendation is based on the fact that partially filled containers of dissolution media did not deaerate as efficiently as full ones. Other parameters such as media volume, gas flow rates, degassing time, analyst variability, and inlet filter pore size were all investigated to determine their effect on the deaeration process. The helium sparging deaeration technique was also effective for deoxygenating other aqueous dissolution buffers. Deaeration by heated vacuum filtration, Dissofill™ (automated heated filtration system),or by inert gas sparging prevented visible bubble formation during the dissolution experiment. However,monitoring of dissolved oxygen levels over the course of an entire dissolution experiment showed that more efficient deaeration of the dissolution media had no discernible effect on the final level of dissolved oxygen.