A collegue did the maintenance of my GC-MS (Thermo Scientific: TraceGC + TraceDSQ) few months ago. I turned it on at the beginning of the week and checked the m/z ratio using helium carrier (high grade). I checked the 18 - 28 and 32 m/z ratio and it gives a lower 18 m/z peak for water than previous check up. I'm a beginner but I suppose it's quite fine. Right ? My main issue is about the intensity. Because on my protocol it's written to wait for an intensity decrease up to 2.10^6. And I spend my all day hoping that decrease but nothing happen (4,7.10^7). So, why does it take so long time ? Is it really important ?

Can anyone help me ?