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21 of 24
Jun 2001
Agilent 6890 Gas Chromatograph Service Manual
Electron Capture Detector (ECD)
340
Troubleshooting contamination problems
the bottom of the hex of the makeup gas adapter. The measurement should
be 19 to 20 mm. If it exceeds 22 mm, the adapter is installed incorrectly.
A ridge inside the cell can prevent the adapter from easily seating all the way.
Wiggle the adapter while installing to allow it to go all the way in. Always
check the nut to hex measurement to be sure.
Evaluate the makeup side
1.
Remove the makeup adapter from the detector. Unscrew the tip and
remove the Gigabore liner. Inspect the adapter body for carbon (graphite)
deposits. Remove all graphite deposits and clean the adapter thoroughly
with methanol. Soak the removable tip in methanol.
2.
Reassemble the adapter
without
the gigabore liner. Install a 5-inch length
of narrow bore column, capped with a new septum, so that the other end
extends 1 mm past the tip of the adapter. Use a Vespel column ferrule
rather than graphite. Tighten the tip just past finger tight with
clean
pliers. Clean the whole assembly with methanol before installing.
3.
Install the capped-off makeup adapter, using a new 1/4-inch Vespel
ferrule. Be sure it is fully seated—check the measurement. Retighten after
the detector has been heated.
4.
Set the makeup flow to the original setpoint and bake out the detector at
350°C for 1 hour. During this time, put the inlet in split mode with 200
to 300 mL/min split vent flow (gas saver off) and bakeout the inlet at
275°C. Bakeout the column at its appropriate temperature.
5.
When bakeout is done,
do not
reconnect the column to the detector. Make
a series of blank runs with the user’s method. If the baseline is
acceptable—free of peaks and humps and under 1000 Hz throughout a
temperature program—then the detector and makeup system are clean.
Any unacceptable baseline problems could indicate contaminated
makeup gas, EPC module, makeup adapter, or detector. These must be
addressed before continuing.
Summary of Contents for 6890 Series
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