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- Posts: 18
- Joined: Tue Oct 20, 2015 5:35 pm
I am working with an Agilent 7890A/7000A in positive CI for the first time and am having an extremely high baseline throughout the entire run. I am fairly experienced with NCI and EI but this is my first time in PCI and I am lost. I'm using methane for the CI source.
The noise ions are 12 or 14 amus apart which means hydrocarbons to me, but I am analyzing a standard in DCM. I know it can come from the fore line pump, but the instrument was fine in EI a few days prior to installing the CI source.
I'm thinking my ionization parameters are too high? I have 80 µA running through the filament. This seems high to me (EI is usually 35) but 80 is the default setting and my manual suggests 150 µA.
Any suggestions would be greatly appreciated