Purging the Pump

When the solvents have been exchanged or the pumping system has been turned off for a certain time (for example, overnight) oxygen will rediffuse into:

the solvent channel between the solvent reservoir,
the vacuum degassing unit (if available in the system),
the pump.

Solvents containing volatile ingredients will slightly lose these components. Therefore, purging of the pumping system is required before starting an application.

Start a purge in the controlling software with a purge flow set to 3 mL/min per channel.

Flush all tubes with at least 15 mL of solvent.

NOTE

Never use the pump to prime/purge empty tubings (never let the pump run dry). Use a syringe to draw enough solvent for completely filling the tubings to the pump inlet before continuing to purge with the pump.

**Table:** Choice of Priming Solvents for Different Purposes
Activity	Solvent	Comments
After an installation When switching between reverse phase and normal phase (both times)	Isopropanol Isopropanol	Best solvent to flush air out of the system Isopropanol is miscible with both normal phase and reverse phase solvents.
After an installation	Ethanol or Methanol	Alternative to Isopropanol (second choice) if no Isopropanol is available
To clean the system when using buffers After a solvent change	Bidistilled water Bidistilled water	Best solvent to redissolve buffer crystals Best solvent to redissolve buffer crystals
Before turning off system for an extended period	50 % methanol or 50 % isopropanol in water, without additives

**Table:** Choice of Priming Solvents for Different Purposes
Activity	Solvent	Comments
After an installation When switching between reverse phase and normal phase (both times)	Isopropanol Isopropanol	Best solvent to flush air out of the system Isopropanol is miscible with both normal phase and reverse phase solvents.
After an installation	Ethanol or Methanol	Alternative to Isopropanol (second choice) if no Isopropanol is available
To clean the system when using buffers After a solvent change	Bidistilled water Bidistilled water	Best solvent to redissolve buffer crystals Best solvent to redissolve buffer crystals
Before turning off system for an extended period	50 % methanol or 50 % isopropanol in water, without additives

If the system has been run dry or air has diffused into the pump, it might require extra steps to get rid of the air again. The following procedure will give the best and fastest results.

Change solvents to isopropanol.
Purge the system with 3 mL/min, composition 50/50 and for 10 min.
Attach a column suitable for isopropanol and set the Max. pressure limit to the limit of the column.
Run the system at composition 50/50 and a flow rate that gives a pressure close to the limit of the column. Turn on the Conditioning function.
Observe the pressure fluctuations. The system is air free when the pressure is stable.
Change solvents and column according to the analytical conditions and purge the system to change solvents.

21-Jun-2025