Chromatography Forum

Dears

This is my pressure curve (Agilent 1100 quat pump). Flow rate is 0.55 mL/min, the pressure spikes are spaced ~11 seconds. I am not completely sure but I think the spikes correlate with each click of the active inlet valve.
But before buying a AIV cartridge or sacrificing seals: What do the experienced guys think which part to replace first?


Kind regards
Jörg

Hello

Few things:

1. Try to run leak test/ pressure test. It will give you more details which pump valve(s) can cause troubles

2.Check compressibility factors for solvents

3.Check degasser

4.If you calculate ripple you will see that it is about 1-2% so it is not far from specification (small pressure drops could be because of AIV cartridge but leak test will prove it)

I'd recommend leak test as very first diagnostic tool

Good luck

Regards

Tomasz Kubowicz

Purge all four channels 10 minutes at 5ml/min and try.

Put all four inlets into the same reservoir, purge all, then see if ripple remains or is gone. If gone, then not the pump itself, suspect mixing valve.

Make sure that the purge valve is not leaking a tad; often these have a waste tube on them so not so easy to see, pull that off.

The pattern shows that it builds pressure quickly then slowly drops off. That would be more like the outlet check valve leaking than the AIV(though it could still be the AIV). If you do the high flow flush mentioned above it could remove any crystals that may have formed on the outlet valve seat or any seal particles that may have lodged there.

Another way to check the mixing valve is to place the lines in four 100ml graduated cylinders and run a flow of 25/25/25/25% at 1ml/min for 40 minutes and see if all lines draw 10ml from their cylinders. If not then you have one of the solenoids sticking or leaking.

What conditions are you showing w/ your trace? If it is (for example) 98%A, 2%B or something similarly lopsided, then this is to be expected from a high pressure mixing system. Your only treatment may be an active mixer (which will add to your gradient delay).

Hi everyone. I ran pressure and leak test. Sorry this is not ChemStation so I cannot show the nice plots but only the log file from Chromeleon.

Pressure test:
[Message] 14:20:43 {Pump} Device notification ( Wait Pressure )
[Message] 14:20:43 {Pump} Measuring the slope of the pressure ramp ...
[Message] 14:21:24 {Pump} Slope of initial pressure ramp > 300 bar/min : 559.8 bar/min
[Message] 14:21:24 {Pump} > PASSED <
[Message] 14:21:24 {Pump} Pressure value > 385 bar : 391.8 bar
[Message] 14:21:24 {Pump} > PASSED <
[Message] 14:21:24 {Pump} Measuring the pressure drop ...
[Message] 14:24:24 {Pump} Device notification ( Aborting active )
[Message] 14:24:24 {Pump} Final pressure drop < 2 bar/min : 2.4 bar/min
[Warning] 14:24:24 {Pump} > FAILED <

Leak test:
[Message] 14:35:35 Wait finished
[Message] 14:36:39 {Pump} Plateau 1 reached
[Message] 14:36:39 {Pump} Pressure value > 100 bar : 139.6 bar
[Message] 14:36:39 {Pump} > PASSED <
[Message] 14:37:39 {Pump} Slope of plateau 1 is > 0 bar/min : -2.2 bar/min
[Warning] 14:37:39 {Pump} > FAILED <
[Message] 14:37:53 {Pump} Plateau 2 reached
[Message] 14:37:53 {Pump} Pressure value > 140 bar : 174.5 bar
[Message] 14:37:53 {Pump} > PASSED <
[Message] 14:38:53 {Pump} Slope of plateau 2 is > 0 bar/min : -2.8 bar/min
[Warning] 14:38:53 {Pump} > FAILED <
[Message] 14:38:58 {Pump} Device notification ( Wait Pressure )
[Message] 14:39:19 {Pump} Plateau 3 reached
[Message] 14:39:19 {Pump} Pressure value > 385 bar : 391.3 bar
[Message] 14:39:19 {Pump} > PASSED <
[Message] 14:42:19 {Pump} Final pressure drop < 2 bar/min : 2.1 bar/min
[Warning] 14:42:19 {Pump} > FAILED <
[Message] 14:42:19 {Pump} Leak test finished

I already suspected the pressure test to fail, no surprise. But I don't know how to interpret the leak test.

DR: This is 90% water/10 % Acetonitrile at 0.55 mL/min.

Regards
Jörg

Hello

I'd recommend pump PM - replace seals (seals in seal wash rings if you have them) and replace AIV catridge then run leak test. If still FAILED replace OBV.

Note: I always run leak/pressure test on 2-propanol (I findd it best solvent for it). Of course other people may have different opinion but it is my personal opinion.

Regards

Tomasz Kubowicz

while pumping, if you observe a bubble that is "stuck" in the skinny AIV out line(to mcgv) i would replace aiv cartridge, not entire valve.
Your plot appears to be an OBV (check valve) issue. remove and sonicate in methanol before purchasing a new one