GCMS Ions, what is what
ions (m/z) |
Compound |
Possible Source |
13,14,15,16 |
Methane |
CI gas |
18, 28, 32, 44 or 14, 16 |
H2O, N2, O2, CO2 or N, O |
Residual air and water, air leaks, outgassing from Vespel ferrules |
31, 51, 69, 100, 119, 131, 169, |
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, |
Dimethylpolysiloxane |
Septum bleed or methyl silicone column coating |
77, 94, 115, 141, 168, 170, |
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, fore line pump oil |