Waters GCT Premier - Page 81

Tuning the instrument for positive CI 3-29
See also: Table titled “Recommended Tuning starting values:” on
page 3-3.
2. Ensure the Limit Rhenium Filament Current check box is selected.
Tip: The rhenium filament is provided with the instrument. However, if
you have fitted a Tungsten filament, then ensure the Limit Rhenium
Filament Current check box is cleared.
3. Click .
4. Set the Emission Current to 250 µA.
5. In the TDC Settings dialog box, set the Veff value to display the correct
mass in the peak display or run the Instrument Setup wizard for this to
be completed automatically for you.
See also:
• Setting up nominal mass on page B-47.
• Setting up the instrument automatically on page 3-8.
6. While monitoring the peak from methane C
2
H
5
+
at 29 Da, tune the
following parameters for maximum intensity for the (MH)
+
(m/z 286) ion
of tris (trifluoromethyl) triazine.
7. Adjust the beam steering in increments of 0.1 V to minimize the low
mass peaks, while maintaining good reference material sensitivity.
8. Optimize the beam steering so that the peak at m/z 29 is minimized
while the peak at m/z 286 is retained.
9. Optimize the focus 2 value to maximize the intensity of the peak at
m/z 286.
10. Optimize the focus 1 and focus 3 values.
Note: Tuning the focus 1, focus 2, focus 3 can affect the beam steering
value.
11. Use the low mass cut-off (LMC) to eliminate the m/z 29 peak and tune
for maximum sensitivity on the m/z 286 peak.
See also: Low Mass Cut-Off on page B-16.
12. Continue to tune the instrument by repeating step 7 through 10 until
you maximize the intensity of the peak at m/z 286.