WATERS CORPORATION 2424, Operator'S Manual, Page: 166 / 196

6-8 Optimizing Detection and Preparing Solvents
that gas in the vapor phase above the liquid. If the partial pressure of a gas on
the surface of the liquid is reduced, for example, by evacuation, then a
proportional amount of that gas comes out of solution.
Tip:
Vacuum degassing can change the composition of mixed solvents.
Ultrasonic agitation
High energy ultrasonic agitation drives energy into the solvent and causes the
submicron-sized “bubbles” of gas to aggregate. As the gas bubbles aggregate,
they become large enough to float out of the solvent and dissipate. Used alone,
ultrasonic agitation degasses 4 liters of solvent in approximately 22 minutes.
Solvent degassing considerations
Select the most efficient degassing operation for your application. To remove
dissolved gas quickly, consider the following.
Vacuum degassing
The longer a solvent is exposed to the vacuum, the more dissolved gases are
removed. Two factors affect the amount of time the solvent is exposed to the
vacuum:
• Flow rate – At low flow rates, most of the dissolved gas is removed as the
solvent passes through the vacuum chamber. At higher flow rates, lesser
amounts of gas per unit volume of solvent are removed.
• Surface area of the degassing membrane – The length of the degassing
membrane is fixed in each vacuum chamber. To increase the length of
membrane, you can connect two or more vacuum chambers in series.
The inline degasser is available as an option or factory-installed in the Waters
Alliance Separations Module, XE model. Standalone inline degassers are also
available.
Sparging
Helium sparging prevents reabsorption of atmospheric gases. Use this method
to retard oxidation when you are using THF or other peroxide-forming
solvents.