Agilent Technologies 5975T LTM GC/MSD, Руководство по устранению неисправностей и техническому обслуживанию

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70 Troubleshooting and Maintenance Guide
3
Chromatographic Symptoms
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 inlet
• 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 4 lists some of the more common contaminants, the ions
characteristic of those contaminants, and the likely sources of
those contaminants.
Table 4 Common contaminants
Ions ( m/z ) Compound Possible source
18, 28, 32, 44 or 14, 16 H
2
0, N
2
, O
2
, CO
2
or N, O Residual air and water, air leaks,
outgassing from Vespel ferrules
31, 51, 69, 100, 119, 131,

169, 181, 214, 219, 264, 376, 414, 426,
464, 502, 576, 614
PFTBA and related ions PFTBA (tuning compound)
31 Methanol Cleaning solvent
43, 58 Acetone Cleaning solvent
78 Benzene Cleaning solvent