74 Agilent 7890 Series Troubleshooting
3 Chromatographic Symptoms
FPD Flame Goes Out During a Run and Attempts to Reignite
If the flame goes out during a run, do the following:
• Check the GC system for leaks, especially at the detector
column fitting. (See “Checking for Leaks”.)
• FPD
+
: Verify the transfer line temperature is set 200 °C.
• FPD: Verify the detector temperature is set
200 °C.
• Ensure that condensation in the vent tube is not dripping
back into the detector. The flexible plastic vent tube must
run from the detector into a container, without sagging, in
order to properly drain water condensate. Keep the open
tube end out of the water in the container.
If the FPD flame goes out and then reignites, do the following:
• Verify that the Lit offset setting is lower than the normal
baseline.
• Check for leaks. (See “Checking for Leaks”.)
• Check the flow settings, then measure the actual detector
flows. (See “To Measure a Detector Flow”.)
• Certain environmental conditions, such as:
• Strong electromagnetic fields
• Large ambient temperature swings
• Large atmospheric pressure swings
can cause an artificially low signal in the GC, incorrectly
indicating that the flame has gone out. As a result, the run
aborts and the GC tries to relight an already-lit flame.
You can verify that the flame is lit by holding a cold, shiny
surface (such as a mirror or a wrench) over the exit tube.
Condensation on the surface indicates that the flame is lit.
Reset the Lit offset to 2.0.
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