To Use Other Reagent Gases - HP 5973 MSD Hardware Manual

 CI operation
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To use other reagent gases

This section describes the use of isobutane or ammonia as the reagent gas. You
should be familiar with operating the CI-equipped HP 5973 MSD with methane
reagent gas before attempting to use other reagent gases.
C A U T I O N Do not use nitrous oxide as a reagent gas. It radically shortens the life span of the filament.
Changing the reagent gas from methane to either isobutane or ammonia changes
the chemistry of the ionization process and yields different ions. The principal
chemical ionization reactions encountered were described in general in the Theory
of operation section in Chapter 2. If you are not experienced with chemical
ionization, we suggest reviewing that material before you proceed.
N O T E Not all setup operations can be performed in all modes with all reagent gases. See the
following table for details.
Reagent gas/
mode
Methane/ PCI
Methane/ NCI
Isobutane/ PCI
Isobutane/ NCI
Ammonia/ PCI
Ammonia/ NCI
64
Reagent ion
masses
a
17, 29, 41
b
17, 35, 235
39, 43, 57
17, 35, 235
18, 35, 52
17, 35, 235
a. There are no PFDTD ions formed with any reagent gas but methane.
Tune with methane and use the same parameters for the other gas.
b. There are no negative reagent gas ions formed. To pretune in nega-
tive mode, use background ions: 17 (OH
These ions can not be used for reagent gas flow adjustment. Set
flow to 40% for NCI and adjust as necessary to get acceptable re-
sults for your application.
Flow adj ions: Ratio PFDTD
Calibrant
ions
41, 267, 599
28/27: 1.5 – 5.0
N/A 185, 351, 449
N/A
57/43: 5.0 – 30.0
N/A 185, 351, 449
35/18: 0.1 – 1.0 N/A
N/A 185, 351, 517
- -
), 35 (Cl ), and 235 (ReO
-
).
3