Pump Problems

<p>Our lab has recently been experiencing problems with the BSM on our Acquity system. The main problem seems to be pressure fluctuation (high delta psi). Removing the check valves and sonicating usually acts as a quick fix, however on these occasions we would then phone the system in to get new check valves fitted. We now seem to be on our third set of check valves in the space of 4 months.</p><p style="height: 8pt"/><p>On other occasions the pumps will fail their leak tests again requiring engineer assistance. In the last 4 months we have had all the seals replaced (twice!) and the pump heads on pump A replaced.</p><p style="height: 8pt"/><p>We can't seem to figue out if we are having a run of bad luck or it something that we are doing causing the pumps to continue to fail.</p><p style="height: 8pt"/><p>Our mobile phases tend to be made up of either 0.1% TFA or 0.1% formic acid for the aq phase and either ACN or MeOH for the organic. All analytical grade. We don't filter our mobile phases unless we are dissolving a buffer. We always try to make sure the system is flushed after running.</p><p style="height: 8pt"/><p>Is there something else that we should be looking out for??</p>


  • lizh


    I do feel that something must have changed, you were OK and now that you are not, so we need to understand what could have changed.

    I would ask if the solvent mobile phase components as changed, supplier or lot? Any new sample types? I would consider particulates contamination. Is there an oversight or a leak with the seal wash. Any method changes that you can think of that could contribute. Any further details would be appreciated.

    Best regards,


  • Hi,

    I am wondering why you are not using, LC grade & 0.2u filtered solvents & still not clear you have high pressure or low pressure problems. As per your description I am suspecting two possibilities 1-your in-line filter/mixer unit is clogged (may cause high pressure, during solvent flow) , 2- your solvent filters are clogged (may cause pressure flu action; low pressure)

    What you do now, prepare 50% 0.2u filtered MeOH, remove all four solvent filters (or replace) & put all lines in 50% MeOH, prime all four lines for 5-minutes & visually inspect whole BSM for leaks, if you didn't find any leak (because you said you already changed many things; check valves, seals), prime again for 3-minutes & visually inspect solvent flowing from vent-A & vent-B; after that do decay & leak test. I hope your test will pass.

    If you still experiencing high pressure during sample run or column wash, you may check your in-line mixer unit (near vent lines).

    ~ SA

  • Hi,

    Our Water and solvents are already filtered through 0.2 um filters as supplied. From what I have read this seems to be acceptable.

    The problem with pressure is neither too high or too low. Just too eratic!

    It seems to happen most when switching over to a different method. ie one user is running their samples duing the day, a second user comes along for an overnight run using a different method. This is where we may see a problem. I have been the principle user of the uplc in our lab for the last two years. I have been trying to get others into the habit of using the acquity however their experience of the uplc seems to be that it is pretty unreliable when compared the Alliances that we have plenty of.

    As far as I am aware we are still on the usual suoppliers of reagents.

    Our engineer seems to think we should spend more time flushing the system but surley this defeats the purpose of the machine in the first place if we are spending ages flushing it.

    The only thing I can think of is that pump B will almost be contantly sitting in strong organic mobile pahse as we only tend to flush of the line that has had the buffer/modifier in it, howveer pump A throws up its fair share of errors as well.

    I will look at the in-line mixer just to check. The machine is working fine just now as we have new check valves in.

    Thanks to those who have offered help.

    I'll monitor the machines use over the upcoming weeks to see if I notice any trends.

    Thanks to those that have offered some help.

  • Hi!

    we had same problems with check valves (we changed two sets in six months...), we think that probably the problem is Acetonitrile.....

    Acetonitrile forms polymers that could settles in check valve and cause pressure fluctuations....

    In the past we usually used the line A for Acetonitrile and the line B for aqueous solvents and we found the check valve damaged on Pump A,

    now we regularly invert line A and B in this way Acetonitrile polymers don' t pile up in the check valves..

    I think also that the check valves on Acquity UPLC could have some design problems in fact the new versions of Acquity UPLC have only automatic check valves!

    Have a nice day!

  • Thank you for this.

    Here is info from an RDE engineer in the pump team...

    JT Baker even mentioned last time he visited them that ACN is contaminated with acrylonitrile which will polymerize into a white flaky material. ACN is a by product from the manufacture of acrylonitirile.

    He further suggests that keeping flow going through the B pump when not in use will also probably help. 0.050 ml/min should be fine.

    Best regards,


  • Thanks for all the suggestions.

    I flushed all lines the other day with 50% MeOH. No leaks. Both pumps gave a delta psi between 2 and 5 which is good.

    I think from now on we will make sure we also flush off pump B with a weak organic mix after use to avoid in build up of any contaminants.