I have a 7890A/5975C with MMI. I have been seeing a huge ghost peak towards the end of my 1st run of the day. It gets smaller in the runs after but never goes away. I have performed basic inlet maintenance, cleaned it, baked it out with the split on 200ml/min. I can't get it to go away. My guess is that its coming from a part of the inlet I cannot see but not sure where. It's being identified as TXIB which is a plasticizer. I have avoided using any plastics near this instrument because of potential phthalate contamination so I cannot think of a potential source. I have made sure that the regulator has a stainless steel diaphragm, changed the copper lines, and even the split vent cartridge. Has anyone run into an issue like this before? Am I missing something? Any insight or thoughts would help.
Thanks in advance.