10-52 Routine Maintenance
Setting the optimum gain for the detector
The optimum gain for the detector is determined automatically when the
Instrument Setup wizard runs. Using the procedure described to determine
the gain of the detector manually.
Note: Before setting the optimum gain for the detector, ensure you
conditioned the detector.
To set the optimum gain for the detector:
1. In the MassLynx Tune window, click Settings > TDC Settings.
2. In the TDC Settings dialog box, set the TDC signal threshold to 40 or a
previously determined value.
3. Click OK.
4. In the MassLynx Tune window, start acquiring data with heptacosa in
continuum at a 0.9 second scan and with an inter-scan delay of
0.1 second, from 50 Da to 650 Da, for a duration of 60 minutes.
5. Set the MCP voltage to 2000 V.
6. Create a chromatogram of the peak at 263 Da.
7. Right-click and drag across the peak at 10%, and view the
chromatogram in real-time as the acquisition progresses.
8. Check that the signal at 263 Da is less than1000 counts per second in
continuum mode, to ensure you are not saturating the detector. If the
signal is greater than 1000 counts per second, open the reference
reservoir pump-out valve to reduce the amount of heptacosa until the
counts per second falls below is 1000.
See also: Effects of saturation on peak shape on page B-51.
9. Increase the MCP voltage in increments of 100 V until the ion count
reaches a plateau in the chromatogram.
10. Check again that the signal at 263 Da is less than 1000 counts per
second in continuum mode, to ensure you are not saturating the
detector. If the signal is greater than 1000 counts per second, open the
reference reservoir pump out valve until the signal is less than 1000
counts per second. Then return to step 9.
11. Set the MCP voltage 50 V lower than the plateau to ensure that all the
ions are counted and excess electrical noise is minimized.
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