48 Troubleshooting and Maintenance Manual
2 General Troubleshooting
Contamination
Contamination is usually identified by excessive background in the mass
spectra. It can come from the GC or from the MS. 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 MS.
Contamination originating in the GC typically comes from one of these
sources:
• Column or septum bleed
• Dirty GC inlet
• GC inlet liner
• Contaminated syringe
• Poor quality carrier gas
• Dirty carrier gas tubing
• Fingerprints (improper handling of clean parts)
Contamination originating in the MS typically comes from one of the following
sources:
• Air leak
• Cleaning solvents and materials
• Foreline pump oil
• Fingerprints (improper handling of clean parts)
Table 3 lists some of the more common contaminants, the ions characteristic
of those contaminants, and the likely sources of those contaminants.
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