Chromatography Forum

Dears

My Agilent 1100 quat pump does not build up pressure any more. With opened purge valve it produces some drops, then the last hanging drop (but not more) is drawn back from the outlet, then it pumps again some drops. Drops come out when the piston on the right side moves forward.
My first idea was the check valve. I replaced the cartridge => same symptom.
Then I exchanged all seals => same symptom.
Where can I look next?

Thanks in advance
Jörg

... My first idea was the check valve. I replaced the cartridge => same symptom.
...
Where can I look next?

I don't know for sure how 1100 pump is built, but probably there is another valve - active inlet valve. Both inlet and outlet valves have to be functional.
And isn't the line feeding the pump with mobile phase clogged ?

Take the column offline. Then pump at 5 mL/minute hot water, then Methanol, then IPA, and back to water. This will solubilize any blockages.

Finally pump water at 1 ml/minute. Do you still have a leak? If so find it (it is usually around where the column is attached).

Dears

My Agilent 1100 quat pump does not build up pressure any more. With opened purge valve it produces some drops, then the last hanging drop (but not more) is drawn back from the outlet, then it pumps again some drops. Drops come out when the piston on the right side moves forward.
My first idea was the check valve. I replaced the cartridge => same symptom.
Then I exchanged all seals => same symptom.
Where can I look next?

Thanks in advance
Jörg

You say no pressure? Even with purge closed? Does not sound like blockage to me, sounds more like air in lines above that purge. Have you checked that? Especially when you say that flow goes backwards briefly. One channel at a time run 100% that channel and 2-3 mL/min flow, watch for bubbles in the line.

Did someone else use the instrument and forget mobile phase and run it dry and not fully prime the instrument before you? Air can be hiding in those lines in a number of places.

Also watch the line of the incoming solvent where it goes into the bottom of the pump. If a bubble there moves forwards and backwards then you could have a bad Active Inlet valve, the solenoid at the bottom where the line attaches. These have a replaceable cartridge, different than the one at the top.

Thank you all for assistance

The outlet valve was the problem. I only replaced the inlet valve cartridge before. Sonicated the outlet valve this morning, now it is working again.

Regards,
Jörg

Thx for feedback.