Agilent Technologies 5975T LTM GC/MSD, Troubleshooting And Maintenance Manual

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Chromatographic Symptoms
3
Troubleshooting and Maintenance Guide 69
Air Leaks
Air leaks are a problem for any instrument that requires a
vacuum to operate. Leaks are generally caused by vacuum seals
that are damaged or not fastened correctly. Symptoms of leaks
include:
• Higher than normal analyzer chamber pressure or foreline
pressure
• Higher than normal background
• Peaks characteristic of air ( m/z 18, 28, 32, and 44 or m/z 14
and 16)
• Poor sensitivity
• Low relative abundance of m/z 502 (this varies with the tune
program used)
Leaks can occur in either the GC or the MSD. The most likely
point for an air leak is a seal you recently opened.
In the GC, most leaks occur in:
• GC inlet septum
• GC inlet column nut
• Broken or cracked capillary column
Leaks can occur in many more places in the MSD:
• GC/MSD interface column nut
• Side plate O-ring (all the way around)
• Vent valve O-ring
• Calibration valve
• GC/MSD interface O-ring (where the interface attaches to
the analyzer chamber)
• Front and rear end plate O-rings
• Turbo pump O-ring