Hi! After many attempts to elucidate what's happening with our Agilent 6495C TQ, I started to wonder if metal ions from some samples can interfere with mass detection in a way that quads going crazy. Literary. And I have sent some samples from my prior runs to ICP-OES colleagues, so here are results for ions that really was in water phase, but migrate at some low level into acetonitrile extract. Only Fe and Cu migrated, because they formed complexes with some aromatics, obviously soluble in organics.

Fe 0.992 mg/kg
Cu 10.9 mg/kg

Because injection volume was 2 uL, there were 1.98 and 21.8 ng of iron and copper in mobile phase heading to mass detector. It was really small quantities, but was it somehow enough to contaminate optics and quads? From service they didn't concluded anything, and responses already went down prior to this runs, but then again. In my personal opinion, there were tons of ions and complexes from pesticides and other crude extracts analyses, but it always went well after routine cleaning. Thanks