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5977b GC-MS Autotune failing. Low count for mass 502 m/z

Question asked by chemist23 on Feb 12, 2020
Latest reply on Mar 10, 2020 by chemist23


The tune evaluation on the 5977B GC-MS is failing. The reason is 502/69 mass ratio is smaller than 2.4 (reading = 1.5-2.0), more specifically the 502 m/z count is around 7000-9000, instead of 20000 which is seen in previous autotunes.

I cleaned the ion source, changed the filament and the next possible error that is showing is leaks or bad vacuum.

I can get H2O down to ~3% and N2 to ~2%. Previously, we been able to get N2 down to 0.8-1.0%, but I only have the vacuum on for ~24 hours to achieve 2%.

Any other possible things I can do to troubleshoot?