66 Troubleshooting and Maintenance Manual
3 CI Troubleshooting
No or low PFDTD signal, but reagent ions are normal
You are using any reagent gas but methane in PCI.
Switch to methane.
Wrong or corrupted tune file loaded
Check your tune file.
No PFDTD in the calibrant vial
Inspect the calibration vial on the back of the flow controller. If necessary, fill
the vial with PFDTD. Do not fill the vial completely; keep the level at least
0.5 cm from the top of the vial.
The pressure of the methane entering the flow controller is too high.
Make sure the regulator on the methane supply is set to 10 psig (70 kPa).
The CI ion source is dirty.
Clean the ion source. See Chapter 5, “CI Maintenance” on page 123 for more
information.
The calibration valve was not purged after the vial was refilled.
Purge the calibration valve as described in “To refill/purge the EI calibration
vial” on page 89. Then clean the ion source.
The calibrant vial was overfilled. Excess PFDTD can quench the chemical
ionization reactions.
Check the level of the PFDTD in the calibration vial. It should be below the end
of the inside tube in the vial.
Poor quality methane (purity below 99.99%)
Replace the methane with high-purity methane. If necessary, clean and purge
the reagent gas lines and clean the ion source.
To Next Page
Loading...
Need help?
General
