General Troubleshooting 2
5977B Series MSD Troubleshooting and Maintenance Manual 61
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 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 MSD typically comes from one of the
following sources:
• Air leak
• Cleaning solvents and materials
• Foreline pump oil (standard foreline pump)
• Fingerprints (improper handling of clean parts)
Table 6 on page 62 lists some of the more common contaminants, the ions
characteristic of those contaminants, and the likely sources of those
contaminants.
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