Hello, I am working on GC/MS (8890 GC-5977B MSD). I run some PAHs (Polycyclic aromatic compounds) using HP-5MS column but the responses of some compounds that have long retention time (high boiling point and high polarity) are very low. I tried raising the MS source and quad temperature but it does not seem significant. Any advice for improve the response? Thank you for your help.