Solvent Degassing Methods - Waters ACQUITY Refractive Index Detector Overview And Maintenance Manual

Effects of intermolecular forces
Nonpolar gases (N
in polar solvents. Generally, a gas is most soluble in a solvent with
intermolecular attractive forces similar to those in the gas ("like dissolves
like").
Effects of temperature
Temperature affects the solubility of gases. If the dissolution is exothermic,
the solubility of the gas decreases when you heat the solvent. If the dissolution
is endothermic, the solubility increases when you heat the solvent. For
example, the solubility of He in H
temperature, but the solubility of He in benzene increases with an increase in
temperature.
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.

Solvent degassing methods

Solvent degassing helps you attain a stable baseline and also improves
reproducibility and pump performance.
There are two common methods used to degas solvents:
• Reducing pressure by vacuum
• Sonication
You can use these methods individually or in combination.
Vacuum degassing
To remove dissolved gasses from the solvent, the in-line vacuum degasser
relies on the principle of Henry's law, which 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.
, O , CO , He) are more soluble in nonpolar solvents than
2 2 2
O decreases with an increase in
2
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