[amol.sagulale]

I recently became involved in a project that used an Acquity UPLC to do the testing.  I have had nothing but trouble with the instruments (3) associated with this project.  I'm not running anything crazy - water and ACN for mobile phase, both are MS grade and directly used out of the bottle.  The water is changed weekly to prevent growth.  The samples are a pharmaceutical mixture in clean solvent which are filtered prior to running.  I see no problem with my set-up so far but over the last six months we have had five seperate issues with the injector, many check valve and seal failures and very inconsistent column performance.  I was wondering if anyone else has had similar issues or if I just have three lemons?  Any thoughts or suggestions would be very appreciated as I am new to UPLC (although I have 10+ years of HPLC experience) and am beginning to wonder if these systems are even worth the hassle.  In six months I haven't had a single week where all three instruments were operational.  It is driving me crazy.

[Arkcon]

OK, from the description of your problem, you have been doing everything correct to try and find the source of the problem.  That's good, but something to remember, when you do many things to nail down a problem, is you may go too fast, and do something sloppy.  That's not an attack on you, I just want you, as you try to fix your problem, try to keep this in mind.  For example, you have HPLC grade ACN in one eluent line, UPLC Grade H₂O in the other.  Are they sealed properly to protect against dust?  And if they're sealed properly, how are they vented so the HPLC pump can pull from them without creating a vacuum?  The same with your sample prep -- are you sure no one in your facility is taking short cuts?

Now, are you sure that your samples are soluble in ACN/water at all proportions that are used in your analysis.  Since your samples are so clean, maybe you can't even tell.  I don't know if your system has some sort of post injector frit, but it may be more important in UPLC than HPLC.

Now, you're describing injector problems, and pump seal problems.  This will require a closer relationship with the vendor.  On some level they rely on you, the user, to teach them what the problems with their systems are.  They may use seal material that they think is solvent compatible, but may fail suddenly.  Also, you have to trust their adjustments are to the correct specifications -- if they clamp down to hard, or unevenly, they can leave you with a system that only works marginally.  When they come to make a service call, you'll want to be near them, and talk to them -- "Are other people having this problem?"  "How is the company making changes to fix this?"  Good service technicians like it when customers take an interest in what they're doing.  And you can try to see if you have a sloppy or poorly informed service tech.

[marquis]

This is a really weird one that caught me once. 

The normal protocol in HPLC is to filter everything.  However, when running certain pharmaceuticals, we weren't allowed to filter at all.

The pharmaceutical was supposed to entirely dissolve. In which case, filtering wasn't needed.   Additionally, the filter interacted with the pharmaceutical.  It actually absorbed the active ingredient onto the filter.  That messed up all the chromatography.

Hope this helps and good luck.