June 11, 2015, 715004754 Rev. A
Page 61
Note: Vacuum degassing can change the composition of mixed solvents.
4.3.2.2 Sonication
Sonication with high-energy sound waves 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. Sonication alone
degasses 4 liters of solvent in approximately 20 minutes.
4.3.3 Solvent degassing considerations
Select the most efficient degassing operation for your application.
4.3.3.1 Vacuum degassing
The longer a solvent is exposed to 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.
When you are using the Alliance separations module with the 2414 RI detector, set
the in-line degasser to “on” degas mode.
4.3.3.2 Sonication plus vacuum
Sonication combined with vacuum degasses solvent very quickly. This technique is
less likely to change the composition of mixed solvents because the mixed solvents
are held under vacuum for only a short time (less than a minute is usually sufficient).
Warning: To avoid injury from flying glass fragments, do not apply vacuum to
the brown glass bottles in which solvent is shipped. There is a high risk of
implosion under these conditions. Use a thick-walled container designed for
vacuum applications.
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