3 Troubleshooting the MSD
Contamination
91
Table 3 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
91, 92 Toluene or xylene Cleaning solvent
105, 106 Xylene Cleaning solvent
151, 153 Trichloroethane Cleaning solvent
69 Foreline pump oil 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 bleed
77, 94, 115, 141, 168, 170,
262, 354, 446
Diffusion pump fluid and
related ions
Diffusion pump fluid
149 Plasticizer (phthalates) Vacuum seals (O-rings) damag-
ed by high temperatures, vinyl
gloves
Peaks spaced 14 amu apart Hydrocarbons Fingerprints, foreline pump oil
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