This Information Applies To: Agilent 8890/8860/7890/7820/6850/6890 GC Systems with TCD (Thermal Conductivity Detector)
Problems observed with thermal conductivity detector (TCD) results can have different underlying causes.
Check that the TCD settings are within the recommended range, then assess the instrument for the following errors/problems:
Hardware Fault Error No signal and/or the GC front panel screen displays Front/Back Detector Error.
Cause: Filament is open (burnt out)
Fix: Replace the TCD detector cell. Contact Agilent Technical Support.
High background causing poor sensitivity
Cause: Contamination of the gas flow system
Drifting or wandering baseline
Cause: Some drift is normal in temperature programmed analyses, but should be reproducible between runs. To determine if the drift is greater than normal compare with established baseline.
Ringing on Peak Tail
Figure 1. Ringing at peak tail
Cause: The sampling rate for the detector is set to equal to or less than 5 Hz (which is the switching rate of the solenoid valve). For more information on sampling rate see Agilent GC Detector Sampling (Data) Rate
Fix: Change the sampling rate to greater then 5 Hz.
Tip: Calibration curves must be re-established after any changes to the sampling rate. In some cases, methods may require re-validation.
Noise/Spikes in Baseline
Fix: Contact Agilent Technical Support for further assistance.
Learn how to effectively operate and troubleshoot your Thermal Conductivity Detector (TCD):
GC-0GEN-1013s - GC Detectors Theory and Operation
GC-7890-2281r - Agilent 7890 Series GC Thermal Conductivity Detector (TCD) Troubleshooting e-learning courses available from Agilent education