Agilent Technologies 5975 Operation Manual page 118

4
Operating in Chemical Ionization (CI) Mode
Table 18
Reagent gas/mode
Methane/PCI
Methane/NCI
Isobutane/PCI
Isobutane/NCI
Ammonia/PCI
Ammonia/NCI
Isobutane CI
Isobutane (C
fragmentation is desired in the chemical ionization spectrum. This is because
the proton affinity of isobutane is higher than that of methane; hence less
energy is transferred in the ionization reaction.
Addition and proton transfer are the ionization mechanisms most often
associated with isobutane. The sample itself influences which mechanism
dominates.
118
Reagent gases
Reagent ion masses
17, 29, 41
17, 35, 235
39, 43, 57
17, 35, 235
18, 35, 52
17, 35, 235
* There are no PFDTD ions formed with any reagent gas but methane. Tune with methane and use
the same parameters for the other gas.
† There are no negative reagent gas ions formed. To pretune in negative mode, use background
ions: 17 (OH-), 35 (Cl-), and 235 (ReO3-). These ions can not be used for reagent gas flow adjust-
ment. Set flow to 40% for NCI and adjust as necessary to get acceptable results for your appli-
cation.
H ) is commonly used for chemical ionization when less
4 10
PFDTD
Calibrant ions
*
41, 267, 599
†
185, 351, 449
N/A
185, 351, 449
N/A
185, 351, 517
5975 Series MSD Operation Manual for MassHunter
Flow adj ions: Ratio
EI/PCI/NCI MSD
Performance turbo
pump
Recommended flow:
20% PCI
40% NCI
28/27: 1.5 – 5.0
N/A
57/43: 5.0 – 30.0
N/A
35/18: 0.1 – 1.0
N/A