Chromatography Forum

Hello, dear forum users,

I have a problem with HPLC Agilent 1100 instrument. I was working with Zorbax SB-C18 column (3.5 mcrn particles) and pressure fell down to 15 bar (very low for this column). After this I wanted to prime the pump, I opened the purge valve and set the flow to 5 ml/min. Then I closed the valve and pressure fell down to 1 bar (now fluctuating to 2 bar sometimes). I checked canals and solvents, actual flow was as set (1 ml/min), wastes are going out as usual. I also checked the seal in pump head (G1311 pump) and it is alright.

Could you please help me and suggest possible problems and solutions?

Hello

Check other modules (sampler and column comartment) for leaks.
This column should give you much higher pressure for 1 ml/min so it looks you have leak somwhere.

Run pressure test for LC stack - plug column compartment with blank nut and check if there is any leak.

Regards

Tomasz Kubowicz

Yes, you have a leak somewhere: external or internal. Don't overlook possible leak through purge valve waste line, often overlooked if connected with tubing to a waste container.

Also it could be a leaking check valve, either the outlet valve or the Active Inlet Valve.

Introduce an air bubble where the solvent lines exits the degasser and with the purge valve closed and pump running with column attached and see if the air bubble is drawn into the pump or if it bounces back and fourth. If it is bouncing it is most likely the Active Inlet Valve allowing backflow instead of pushing solvent on through the pump. If the bubble just sits and doesn't move it would more likely be the outlet check valve, which is allowing backflow from the column into the pump instead of drawing in solvent from the degasser side.

Hello Gulyaim ,

You stated '' wastes are going out as usual '' , do you mean that you checked out the detector outlet and the solvent coming out ?

If this is the case , the pressure sensor may be faulty.

Run pressure test for LC stack - plug column compartment with blank nut and check if there is any leak.

Yes: isolate where the leak/low pressure is. So start with pump module only, blank off the outlet and check pressure for holding/increasing.