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Detectors
1. Make sure the FPD is at operating temperature before trying to light.
2. Remove the rubber drip tube while lighting the FPD.
3. Increase air supply pressure by 10-20 psi.
4. Check the detector gas flows to see if they match the Recommended Gas Flows table.
5. Check the detector output when you turn the flame on. The photomultiplier will see
the glow of the igniter and jump to about 68000 pA.
6. Remove the column and check the tip for residue or burnt polymide coating. If it
appears damaged, cut off the damaged portion and reinstall to the proper height.
7. Remove the igniter glow plug. If dirty or damaged, replace it.
You can tell if your FPD is lit by checking the detector "Output" and "Flame" on the
display. The detector senses that the flame is on by comparing the output with the offset.
An optimized FPD normally runs with an output in the range of 30 to 80 with the offset
set point at 2.0. If the flame is out and the electrometer is on, the output usually displays
less than 1.
Most FPD ignition problems are caused by incorrect gas flows, incorrect column
installation, or a dirty or defective igniter. To troubleshoot:
Less common problems include leaks, quenching, and condensation:
• Large air leaks at the inlet or detector can reduce the percentage of the hydrogen-air
mixture at the detector and cause ignition problems.
• Large injections of certain samples can cause flameouts or quenching that cause the
detector to attempt to relight, interrupting your analysis.
• Condensation is a by-product of the burning of your sample. For many analyses, the
liquid is collected from the vent tube. If the liquid drips back into the detector, it will
extinguish the flame. Agilent recommends that you wait to light the flame until the
detector is at temperature and equilibrated.
• Light leaks at the vent tube can cause a higher baseline offset. Make sure the vent tube
ferrule seals tightly against the emission block. Keep the lid closed over the detector.
Helium is not a good makeup gas
for the FPD. You will not be able to
light or keep the detector lit in the
sulfur mode with helium.
Tips & Tools
Flame Ignition Problems
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