Chromatography Forum

I'm helping a colleague get an Agilent 1100 HPLC running again. The A-side pump wouldn't prime. We changed the seals and it still wouldn't prime. We took out the outlet check valve and sonicated it in water. After assembly, the pump head started pumping liquid but only about half of what we told it to pump via the software. We took off the active inlet to the pump, removed the valve cartridge and sonicated that in water. After assembly, it still is only pumping about half of the flow that we told it to pump (2.5 mL/min, measured with a graduated cylinder out of the waste line/purge valve).

Anybody have an idea what might be going on here? Valve cartridge replacement? Thanks for your insight!

Make sure solvent is not leaking out through a faulty purge valve.

I don't see it coming out anywhere. We measured the flow out of the waste stream for the purge valve. B side is right at 5 mL in a minute. A side is 2.5 mL in one minute when we set it at 5 mL/min in the software (Openlab).

Do you have solvent filter on A line - it can be cloged, for test just remoce it.

Bypass degasser anything changed?

When bypassing degasser introduce the air bubble before the pump. Does bubble move up and down (problem with primary chamber of A channel most probably scratches in balls of AIV cartridge or else malfunction AIV valve) switch B channel AIV valve with B channel. Did problem move to other channel?

When flow is only half of what it should be out of a specific pump head, then one of the two pistons is not working (broken inside seal). Inspect pump.

If the problem has not been described accurately, then I would check the AIV function on BOTH pump heads, individually, with pure solvent (i.e. IPA) only. Verify each pump head has been properly primed, is not restricted (clogged solvent pickup filter) and has fully degassed solvent inside it (many auction purchased pumps have damaged AIV's).