Microcell Electron Capture Detector (Uecd) Noise And Sensitivity; Display Signal Evaluation - Agilent Technologies 7890 Series Troubleshooting Manual

Microcell Electron Capture Detector (uECD) Noise and Sensitivity

C A U T I O N
WA RNING

Display signal evaluation

Agilent 7890 Series Troubleshooting
Detector disassembly and/or cleaning procedures other than
thermal should be performed only by personnel trained and licensed
appropriately to handle radioactive materials. Trace amounts of
radioactive 63 Ni may be removed during these other procedures,
causing possible hazardous exposure to radiation.
To prevent possible hazardous contamination of the area with
radioactive material, the detector exhaust vent must always be
connected to a fume hood, or otherwise vented in compliance
with local regulations.
Performance problems associated with the ECD include (but are
not limited to) loss of sensitivity (real, or perceived), high signal
background, noisy baseline, and chromatographic peaks or
humps that are not characteristic of the samples being injected.
If the problems are not accompanied by an increase in the signal
output, as read from the front keypad of the GC, then suspect
the detector only after the other parts of the chromatographic
system have been checked.
Before starting extensive troubleshooting, consider first the
nature of the problem:
1
If recent changes were made in the system, such as changing
carrier or detector gases, performing inlet or column
maintenance, or changing the column, investigate the
possibilities that contamination or leaks were introduced.
2
If the problem has been chronic and is now acute enough to
interfere with analysis, suspect contamination, column
degradation, or ultimately a bad ECD cell.
See also:
"Display signal evaluation"
"Sensitivity"
The first consideration is the signal value when the GC is in the
idle state. The "idle" signal level is a function of the type and
quality of the carrier and detector gases, as well as the flows
Chromatographic Symptoms
3
63