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GC/MS Systems
Common Contaminants
Ions (m/z) Compound Possible Source
13, 14, 15, 16 Methane CI gas
18, 28, 32, 44 or 14, 16 H
2
0, N
2
, O
2
, CO
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
91, 92 Toluene or xylene Cleaning solvent
105, 106 Xylene Cleaning solvent
151, 153 Trichloroethane Cleaning solvent
69 Foreline pump fluid or PFTBA Foreline pump oil vapor or
calibration valve leak
73, 147, 207, 221, 281, 295,
355, 429
Dimethylpolysiloxane Septum bleed or methyl silicone
column coating
77, 94, 115, 141, 168, 170,
262, 354, 446
Diffusion pump fluid Diffusion pump fluid and related
ions
149 Plasticizer (phthalates) Vacuum seals (O-rings) damaged
by high temperatures, use of
vinyl or plastic gloves
Peaks spaced 14 amu apart Hydrocarbons Fingerprints, foreline pump oil
MSD Contamination Identification
The following table lists some of the more common contaminants, the ion characteristics
of those contaminants, and the likely sources of those contaminants.
Even preconditioned ferrules
can shrink slightly at very high
temperatures, so if leak problems
persist upon a new column
installation, check this fitting first.
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