2000 MS Hardware Maintenance
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Chemical Ionization Options
8. While observing the spectrum using Adjust CI Gas, turn the CI needle valve for
the selected channel on the MCI Module clockwise to increase (or
counterclockwise to decrease) the amount of reagent until the reagent ions
abundances meet the requirements outlined for the chosen reagent in the table
shown in
Ion Intensities for Standard CI Reagents
.
Building GC/MS Methods to Use Different CI
Reagents
The MCI Module may be used in several different ways to acquire data on a
sample for qualitative identification. In general it is advisable to develop a
standard GC and EI Method for data acquisition; then to modify the existing
method to acquire data in each selected CI mode.
NOTE: Acquisition with each CI reagent using the MCI Module requires a unique
GC/MS method. The GC section of the method MUST contain
External Events
programming
to select the CI reagent in Channel A, B, or C. The MS section of
the method MUST have CI mode selected
with the appropriate CI Tune File
.
Preparing a Standard GC/EI/MS Method
Whether you are going to run methods development on single samples or on a
series of samples, it is generally advisable to prepare GC and MS methods for
EI/MS acquisitions first.
This example shows GC method development for the 3800 GC. The
development of the method for 3400/3600 GCs is similar. In the Saturn Windows
Workstation, open a GC/MS method for editing and save it as EI_GC.mth. In the
Methods Directory, choose the item GC Injector. Enter 260 as an isothermal
injector temperature. (It is assumed that you are using a 1079 injector.)
Next, choose the Method Directory item Flow/Pressure and verify that the
parameters are acceptable. The following method uses a Type 1 EFC and
constant pressure programming at 10 psi:
