HPLC degasser techniques: Types of solvent degassing

In HPLC degassing of solvents, mobile phase is very essential for proper operation and retrieval of uniform data.

Degassing removes entrapped air bubbles from the solvents. Improper degassing leads to many problems like fluctuation in pressure, improper peaks, improper detection, clogging of column etc.

Degassing is done by degasser techniques like ultra sonication, filtration etc.

Ultrasonication degassers: Here gas is removed by either bursting of gas bubbles immersing ultra sonic generator into the solvent or by placing the solvent container into ultra sonicator tray. This is the commonest technique for degassing of HPLC solvents.

Filtration degassing: This is not a commonly used technique but is highly effective one.

Here solvents are degassed by synergistic action of vacuum suction, filtration and also mechanical stirring.

The solvents are filtered under vacuum into a filtration flask through a 0.4 to 0.2 micron filter. This provide effective filtration plus exposure of entrapped air to vacuum during passage of solvent through filter pores.

Then the filtrate in the flask is subjected to rigorous stirring using magnetic stirrer with constant application of vacuum for definite period of time (half an hour is recommended). This provides effective degassing as the entrapped air forms bubbles due to stirring and there by removed by vacuum.

This method provides high quality degassing over the sonication method as it not only involves degassing but thorough filtration.

Further it is recommend to put the degassed solvents in refrigerator over night if your mobile phase is not a crystallizing buffer at low temperature. Cold enhances effective degassing.