June 11, 2015, 715004752 Rev. A
Page 146
C.6.1.3
Effects of partial pressure
The mass of gas dissolved in a given volume of solvent is proportional to the partial
pressure of the gas in the vapor phase of the solvent. If you decrease the partial
pressure of the gas, the amount of that gas in solution also decreases.
C.7 Solvent degassing methods
This section describes the solvent degassing techniques that will help you to attain a
stable baseline. Degassing your solvent also improves reproducibility and pump
performance.
You can use either of the following methods to degas solvents:
•
Sparging with helium
•
Vacuum degassing
C.7.1 Sparging
Sparging removes gases from solution by displacing dissolved gases in the solvent
with a less soluble gas, usually helium. Well-sparged solvent improves pump
performance. Helium sparging brings the solvent to a state of equilibrium, which may
be maintained by slow sparging or by keeping a blanket of helium over the solvent.
Blanketing inhibits reabsorption of atmospheric gases.
Sparging can change the composition of mixed solvents.
C.7.2 Vacuum degassing
The in-line vacuum degasser operates on the principle of Henry’s Law to remove
dissolved gases from the solvent. Henry’s Law states that the mole fraction of a gas
dissolved in liquid is proportional to the partial pressure of 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.
Vacuum degassing can change the composition of mixed solvents.
C.7.3 Solvent degassing considerations
Select the most efficient degassing operation for your application. To remove
dissolved gas quickly, consider the following.
C.7.3.1
Sparging
Helium sparging gives stable baselines and better sensitivity than sonication in a
detector, and prevents reabsorption of atmospheric gases. Use this method to retard
oxidation when you are using tetrahydrofuran or other peroxide-forming solvents.
Summary of Contents for 2489
Page 2: ...June 11 2015 715004752 Rev A Page ii...
Page 8: ...June 11 2015 715004752 Rev A Page viii...
Page 14: ...June 11 2015 715004752 Rev A Page xiv...
Page 46: ...June 11 2015 715004752 Rev A Page 46...
Page 124: ...June 11 2015 715004752 Rev A Page 124...
