Bake Out the Agilent Thermal Conductivity Detector

Answer

This Information Applies To: Agilent GC Systems with thermal conductivity detector (TCD)

Issue

Baking the thermal conductivity detector (TCD) at high temperatures can remove sample contaminants that have deposited on the detector surfaces. 

Items Required 

• Ferrule, no hole (p/n 5190-4054) 
• Column nut, any of the following:
  • Column nut, universal (p/n 5181-8830)
  • Blanking plug, finger-tight style (p/n 5020-8294)
  • Finger-tight column nut (p/n 5020-8292)
  • Column nut, collared, self-tightening, inlet/detector (p/n G3440-81011) 
• TCD capillary adapter and fittings (for 7890 and 7820A GC systems)
  • Capillary column adapter (p/n G1532-80540)
  • Nut, 1/8 inch, brass (p/n 5180-4103)
  • Ferrule, 1/8 inch, 15% graphite/85% Vespel (p/n 0100-1332)

Steps to follow

Caution: If the column is not installed, you must turn off the TCD filament and cap the detector column fitting to prevent irreparable damage to the filament caused by oxygen entering the detector.

1. Load the normal GC method and wait for the GC to become ready. 

2. Note the value of the FID signal output for comparison with value after the bake-out. 
   

   • 7890 GC Systems: On the instrument front control panel, press [Front Det] or [Back Det] then scroll to output.
   • 7820A GC Systems: On the Agilent software keypad (remote controller), click [Front Det] or [Back Det] then scroll to output.
   • 8890 GC Systems: On the touch screen or the browser interface, go to Home > Status listing > +Add. Select the detector’s output from the drop-down list, then select Add.
   • 8860 GC Systems: On the browser interface, go to Home > Status listing > +Add. Select the detector’s output from the drop-down list, then select Add.

3. Determine if you need to remove the column. The detector bake-out temperature is 375 °C and the column temperature is 250 or 25 °C above the normal maximum operating temperature. If the upper temperature for the column is less than the bake-out temperature, remove the column, otherwise, jump directly to step 4:

   1. Turn off the TCD filament
   2. To cool the oven and detector, load the GC maintenance method.
   3. Remove the column from the detector.
   4. Cap the detector connection with the column nut and the no-hole ferrule. For the 7890 and 7820A TCD detectors, make sure that the capillary adapter is installed.  
   5. Turn off the carrier gas and remove the column from the GC inlet and go to step 5.
      

      Warning: If using hydrogen as a carrier gas, turn off the hydrogen supply and remove the column to prevent an oven explosion.

       
4. Turn off the TCD filament 
5. Load the normal operating flows. If the column has not been removed from the GC inlet, maintain inert carrier gas flow through the column.
6. Set the reference gas flow rate between 20 and 30 mL/min.

7. Set the temperature zones to the bake out temperatures:

   Caution: Do not exceed the column manufacturer's recommended temperature, as it will damage the column. If the bake out temperature exceeds the recommended temperature, remove the column and turn off the inlet gas flows.

   1. Set the detector temperature to 350 to 375 °C, or 25 °C higher than the normal operating temperature

   2. Set the oven temperature to 250 or 25 °C above the normal maximum operating temperature. Do not exceed the inlet temperature. 

   3. If the column is still installed, set the inlet temperature to 250 or 25 °C above the normal maximum operating temperature. Do not exceed the column maximum temperature. To bake out the GC inlet see How to Bake-out the Split/Splitless Inlet (S/SL) on Agilent GC Systems .

8. Hold at the bake out temperature for several hours

9. Allow the instrument to cool and reinstall the column if appropriate.

10. Load the normal analytical method and allow the system to equilibrate.

11. Check the TCD output value. It should be lower than the first reading. Without a column installed, a clean system baseline should be < 20 pA. If it is not, contact your Agilent service center.

Learn how to effectively operate your Agilent GC Detector: GC-0GEN-1013s - GC Detectors Theory and Operation e-learning course available from Agilent education