To Use Other Reagent Gases - Agilent Technologies G7035A Operation Manual

4
Operating in Chemical Ionization (CI) Mode

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 5977 Series MSD with
methane reagent gas before attempting to use other reagent gases.
Do not use nitrous oxide as a reagent gas. It radically shortens the life span of the
CA UT IO N
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 are described in general
in the 5977 Series Concepts Guide. If you are not experienced with chemical
ionization, we suggest reviewing that material before you proceed.
Not all setup operations can be performed in all modes with all reagent gases. See
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Table 19
Table 19 Reagent gases
Reagent gas/mode
Methane/PCI
Methane/NCI
Isobutane/PCI
Isobutane/NCI
Ammonia/PCI
Ammonia/NCI
* 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 cannot be used for reagent gas flow adjustment. Set the flow to 40% for NCI and adjust as
necessary to get acceptable results for your application.
106
for details.
PFDTD
Reagent ion masses Calibrant ions
*
17, 29, 41 41, 267, 599
†
17, 35, 235 185, 351, 449
39, 43, 57 N/A
17, 35, 235 185, 351, 449
18, 35, 52 N/A
17, 35, 235 185, 351, 517
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
5977 Series MSD Operation Manual