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3 Troubleshooting the MSD
Contamination
Contamination
Contamination is usually identified by excessive background in the mass spectra.
It can come from the GC or from the MSD. The source of the contamination can
sometimes be determined by identifying the contaminants. Some contaminants
are much more likely to originate in the GC. Others are more likely to originate in
the MSD.
Contamination originating in the GC typically comes from one of these sources:
• Column or septum bleed
• Dirty injection port
• Injection port liner
• Contaminated syringe
• Poor quality carrier gas
• Dirty carrier gas tubing
• Fingerprints (improper handling of clean parts)
Contamination originating in the MSD typically comes from one of the following
sources:
• Air leak
• Cleaning solvents and materials
• Diffusion pump fluid
• Foreline pump oil
• Fingerprints (improper handling of clean parts)
The following table lists some of the more common contaminants, the ions charac-
teristic of those contaminants, and the likely sources of those contaminants.
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