Obtaining A Beam In Negative Ci Mode - Waters GCT Premier Operator's Manual

4. In the Tune window, click
5. Increase the detector and the TOF flight tube voltages to the previously
determined operating voltage over a period of 20 seconds. Doing so
minimizes the risk of discharge and possible damage to the detector.
Purging the CI gas lines
Before introducing the CI reagent gas, the internal gas lines must be purged
of air.
See also: Setting up and purging the CI gas lines on page
Introducing CI reagent gas
The pressure of CI reagent gas in the source is usually somewhat lower for CI
negative mode compared to CI positive mode, however this can be compound
specific.
Start with a set pressure read from the source Penning gauge of 5 to
8e-5 mbar.
Introducing CI reagent gas on page
See also:

Obtaining a beam in negative CI mode

To obtain a beam in negative CI mode:
1. Close the reference reservoir pump valve on the top of the instrument.
2. Introduce 0.2 µl of heptacosa via the reference reservoir inlet cap.
See also:
reservoir inlet cap: on page
3. In the Tune window CI Tune tab, set the Emission Current to 250 µA.
4. Set all other source tuning parameters to those provided in the
titled "Recommended Tuning starting values:" on page
previously stored parameters if available.
5. Set the peak display 1 mass range from 448 to 454 Da, and adjust the
gain of the peak display until ions from 451.97 of heptacosa can be
detected.
3-32 Tuning the Instrument
Introducing the reference compound into the reference
3-6.
.
3-26.
3-26.
Table
3-3. Recall