3-28 Tuning the Instrument
6. Right-click in the peak display and click Intensity > Normalize Data.
Result: The peak display is scaled to the value of the intensity of the
highest peak.
Tuning CI gas peaks
To tune CI gas peaks:
1. From the Tune window, clear Low Mass Cut Off check box in the TDC
Settings dialog box.
2. In the CI Tune tab, type the recommended starting parameter values for
tuning, or specify previously saved parameters.
See also: Table titled “Recommended Tuning starting values:” on
page 3-3.
3. Monitor the CI gas ions.
Tip: For example, if you are using methane, note that methane peaks
are viewable at m/z 17, 29 and 41.
4. Increase the flow of CI gas until you achieve the required CI conditions.
Tip: In the peak display, m/z 16 should almost disappear, and the
intensities of peaks at m/z 17 and 29 are optimized.
Obtaining a beam in positive CI mode
As a prerequisite to obtaining a beam in positive CI mode, you must perform
these tasks:
• Setup and purge CI gas line (see Setting up and purging the CI gas
lines on page 3-26).
• Introduce the reagent gas (see Introducing CI reagent gas on page 3-26).
•CI tuning setup (see Setting up for CI tuning on page 3-27).
• Introduce the reference sample (see Introducing the reference sample on
page 3-6).
To obtain a beam in positive CI mode:
1. In the Tune window CI Tune tab, enter the recommended starting
parameter values, or specify previously saved parameters.
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