Chromatography Forum

Hi all,
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? Anyone ever heard of PP vial caps causing a blockage in the FTN?

Thanks!
~max

I also work with an I-class with FTN injection. I don't have experience with the same issue though. What kind of extracts are you injecting, and what is the injection volume? It's better to be safe than sorry and always filter as a last step in sample preparation, even more important when injecting larger volumes.

During installation and training, Waters stressed that we need to use vials with pre-slit septa, or septum parts will clog the needle from time to time. Do you use caps with pre-slit septa?

Remember that you can isolate the problem to the needle / needle seat by performing a "needle seat readiness test" in the software.

Thanks for the reply.
I work with environmental SPE extracts with an inj vol of 2uL and I always use pre-slit PP caps from Waters or Phenomenex. The SM-FTN hasn't failed a needle seal readiness test yet after backflushing and freeing the blockage, which seems to indicate that it's a problem that's introduced during the run itself.

~max