1100 Binary Pump Noise

[bisnettrj2]

This morning I was greeted by a new and troubling noise coming from one of my binary 1100-series pumps. For those of you that work with Agilent 1100's, you know the healthy and regular 'clicks' of the pumps. This was a click, but an abnormal one. I could hear the 'normal' clicks (the up and down stroke of the pistons), but there were additional, rapid-fire clicks, like a 'click-click-click' in a quick beat to the normal 'click....click....click....' of the regular 1100 pumping system. Accompanying these extra clicks was a relatively noisy baseline.



In red is the good baseline, in blue is a later injection with the pump doing it's erratic 'clicking' thing. This is an injection of the same vial about 15 hours apart.

I got the pump to stop making the extra noise by opening the purge valve and purging each channel for 10 minutes at 5 mL/min, then resetting to 1 mL/min and resuming the run and evaluating the baseline. The extra 'clicks' went away, and the baseline returned to normal.

Has anyone heard their 1100-series pump making a noise like this? I didn't notice any sort of wild pressure fluctuations - in fact, a pressure trace overlay is almost identical - flat and regular - even though the baseline on one injection is good and the other is noisy. I'm concerned I'm seeing something that is indicative of an impending catastrophic failure, and I'd like to head it off at the pass (even though I hate that cliche) before it becomes an unserviceable issue.

[Consumer Products Guy]

Red's a GOOD baseline? Then your standards and samples must have nice high absorbances, so baseline doesn't matter much. Because both look pretty bad to me, if you're looking at something with smaller absorbances.

Can you do a "no inject run" and look at its baseline? Have you made new mobile phases? Is your degasser OK? Have you just tried a long capillary to bypass the column?

Agilent pumps and autosamplers can make lots of little noises, but those don't seem to affect their operation any, at least for us.

[bisnettrj2]

Thanks CPG. The red baseline looks fine to me (of course, I've no formal training and I've only worked in one lab, so maybe I'm wrong - it's happened before and will again ). That's my lowest calibration standard - 100 uL of a 0.01 ppm standard. My reporting limit standard is 5-10x higher than this point. I don't think I have any degasser issues (no red LED for that matter) and the pump recently passed a leak test (Chemstation Diagnostic View, IPA, etc.). This noise was pretty loud - as soon as I got near my LCs, I could tell that this one had something wrong. If you look at the 5 peaks near the end of the run, you can tell that the red baseline shows normal peaks, while the blue baseline peaks are jagged and mis-shapen.

If I get a chance today I'll see if I can install a restriction capillary, get it back to the pressure it's currently at, and monitor the baseline. I just found the extra clicking to be disconcerting, and was hoping someone might have had a similar experience.

[bisnettrj2]

I think I might have found the problem. I re-ran the Leak Test and noticed that one of the ramps was almost failing on the "A" side of the pump. I pulled the pump head, and one of the pistons was stuck in the pump head where the piston meets the housing assembly. There was some sort of material built up on the base of the housing assembly and the head of the piston - almost like it was lime scale. I pulled the "B" side (methanol side), and both pistons were stuck - same material. I soaked the pump parts in a solvent mixture (acetone:methylene choride:hexane:toluene), then in a dilute acetic acid (~0.2%) solution, scrubbed off the material with a toothbrush I keep around, replaced the seals in both pumps and the pistons in the A pump, re-ran the Leak Test, passed with flying colors. I'm keeping my fingers crossed that this was the solution - baselines from last night's runs look good (so far). Now I'm wondering where that 'material' came from in the first place, as I'm running Millipore water and HPLC-grade methanol on the A and B channels respectively, no buffers or anything else 'weird'. Something to keep an eye out for in the future, I guess.

[bisnettrj2]

Update on this issue. Eventually, the LC had a pump drive motor error, indicating a pre-pressure sensor over-pressure condition, or a mechanical problem with the pump drive. I replaced the check valves, the pump head, and the main board. The now horrendous noise continued, indicating a failing pump drive assembly. I sent the pump in to Agilent bench repair, and they ended up replacing the pump drive assembly and the pulse damper. I just reinstalled the pump this afternoon (after having switched it out for another binary pump I have). I'll hope I'm never greeted again by the awful pump noise I heard when this problem first reared its head.

[tom jupille]

bisnettrj2, thanks for posting this (and especially thanks for the follow up!). This is a great lesson in the need to be "tuned in" to how our instruments are functioning -- including what they sound like!