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Setting Parameters for Chemical Ionization
After selecting a standard reagent (methane, isobutane, acetonitrile, or
methanol), the CI parameters for the selected reagent are set automatically so
you do not need to change the default values of the CI parameters. However, the
remaining CI parameters (Reaction Storage Level, Ejection Amplitude (V), and
Max Reaction Time) can be optimized for sensitivity. After adjusting these
parameters, click
Save
. You will be prompted for a name under which to save the
modified values.
Reagent Low Mass
is the lowest mass stored in the trap during ionization.
Reagent High Mass
is the highest mass stored in the trap during ionization. All
masses above this mass are ejected during the ionization step. This reduces the
number of EI generated ions that are in the trap.
The combination of
Reagent Low
and
Reagent High Mass
and
Reaction
Storage Level
allows for the selection of a specific reagent ion in the CI process.
For example, only mass 29 of methane could be used as the reagent ion by
ejecting mass 41 during ionization and by reacting at a mass greater than 19 in
the reaction step.
NOTE: When a reagent ion that is formed through a complex process, such as
+
5
2
H
C
formed by the reaction of
+
4
CH
with neutral
4
CH
, both ions must be
within the High and Low mass range.
Reaction Storage Level
is the value of the smallest mass stored in the ion trap
during the reaction period. The optimum Reaction Storage Level will depend on
Summary of Contents for 4000 MS
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