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- Posts: 164
- Joined: Sun Oct 04, 2009 6:18 pm
I have been running a new 5977B recently running low level PAHs, using DFTPP criteria in method 8270C, 8270D, and 8270E. I could easily get DFTPP to pass day after day, sometimes I would have to do normal tweaking of lenses, peak widths, etc. My chromatography was a bit poor, especially for the heavy PAHs. This was odd because I run a 5975C with identical conditions, with virtually no peak tailing.
So I decided to open everything up. I swapped out the Zebron column for a Restek Rtx-5Sil MS, and I cleaned the source. That's when I discovered the 3mm drawout plate. So I swapped it for a 6 mm plate because I knew it would give me better PAH peak shape.
Now my chromatography is great, but I can't get a tune to pass. Problem ions are 68 and 441. Peak shape in manual tune profile view shows significant fronting of 414 and 502. Tune evaluation shows 502 precursors at 10%, which is acceptable by the evaluation guidelines, but I know it's not good. My 5975C is at 2%.
I have now cleaned and reinstalled the source 3 times and I cannot improve peak shape for 502. Not sure what else to do...
Christian