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- Posts: 1
- Joined: Fri Jul 22, 2011 2:45 pm
Instrument: Agilent 1260 with ELS-D
Runs one method for one product 99% of the time, a standard 40-95 gradient of ACN and Water, both 0.1% formic acid modified. Reverse phase, C18 column.
Product we test is a standard mixture of 7-12 peaks, all identified via pure standards and quantified via calibration curves. Method has run with great repeatability and reproducibility for over 1 year.
~3 weeks ago, all retention times shifted ~5.5 minutes downfield with no explanation. No change to column, plumbing, operating pressure, solvent, etc... Fine, I rerun calibration curves based on new retention times, method runs under new retention times until today, when the peaks shifted BACK 4.5 minutes, nearly to where they were originally. I am at a complete loss. I'm looking for any and all ideas, no matter how crazy. Ghosts? Sabotage? anything,