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- Posts: 19
- Joined: Mon Feb 06, 2012 9:53 pm
I'm measuring propiconazole by triple quad LC/MS using a Shimadzu 8060. I've noticed that there is a persistent background for this analyte, typically around 0.2 - 1 ng/mL. I have looked at every possible MRM transition I can find and it always matches propiconazole exactly in terms of ion ratios an retention time.
This happens with just gradient/no injection runs as well. Flushing the LC system with IPA/MeOH/MeCN has no effect, and neither does changing the column. Furthermore, the intensity is highest with the first injections. This all suggests that it is a contamination in the mobile phase or system tubing, but it would be very odd to have a residual pesticide in those.
I've seen data from other labs and other instrument manufactuers where people see the same thing. Anyone have a similar experience, and if so, were you able to fix it? We're trying to move this analyte to GC/MS (where this problem does not exist) but we lose a lot of analyte in our cleanup step and cannot seem to achieve the sensitivity we need.
Thank you!