Media should ideally be prepared and degassed per USP specifi cations. Per USP, the media should be heated to 45o C (although references for 41o C and 41-45o C are found in different USP documents), then vacuum
degassed through a 0.45 μm PVDF filter, and then held under vacuum for an additional fi ve minutes. This procedure essentially is boiling the media at a lower temperature under
a vacuum which effectively removes dissolved gases in the media. If using an alternate degassing step, it should be verified to achieve similar levels of degassing using a dissolved gas meter to demonstrate that <6 ppm oxygen (7) is achieved. One of the
most common degassing procedures used is helium sparging. This can be an effective way to remove gases from the media by replacing them with a more inert gas, helium. This method is generally acceptable for use with the PVT as long as the helium is
sparged with a consistent fl ow rate, a specifi ed diffusion system, such as airstone, for adequate period of time. A sparging level involving at least 15 minutes with a fl ow rate of 4-6L/ minute with an airstone equipped on the inlet to ensure reproducible and
full deareation of the media was found effective in the Agilent studies, and requires validation against the USP method. Other alternatives including sonication and nitrogen sparging are not effective for use with dissolution. Sonication and sonication under vacuum do not work well for aqueous-only media. Nitrogen sparging is replacing air
with its largest component which can actually increase dissolved gas relative to untreated media, and bubbles are usually present after these methods are employed.