Acquity I-class continues to over pressure

I work with an Acquity Iclass BSM and SM that has been having an issue with over pressuring. My solution has been to backflush the needle and needle seal which frees the occlusion (I am able to see a pressure spike before it goes back to baseline), but the issue recurs after a small number of injections (20-30). The problem persists despite changing columns, needles and needle seals, mobile phases, pre-filtering mobile phases, and adding a frit before the isolator column. I'm ready to rule out the mobile phases as the culprit and am thinking it's got to be the extracts themselves or something with the FTN and seal port assembly. I'm working on finding ways to filter the extracts - any possible leads on the occlusion coming from the seal port itself? Ever heard of PP vial caps causing a blockage in the FTN?



  • Hi Max,

    It is very unlikely that the FTN is coreing you vial caps.  The needle is designed to not do that.  Is you sample diluent compatible with the mobile phase?  You could try increasing the size of the "air gap".


    You could also try searching the Waters Knowledge Base for other suggestions -

  • Thanks Marc, all of our mobile phases and buffers are compatible with our sample diluent, this is a recent problem that's cropped up running with the same parameters as previous sequences that have worked great. I'm not sure exactly how increasing the air gap might help, but it's certainly worth a shot in the dark. Thank you,

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