Chromatography Forum

I am running a HP 6890A GC/MS

The GC has a MS on the side, FID and TCD.
Recently we have taken out a PDD and put a new FID detector. Afterwards
the TCD showed spiking whenever we ran something (even on Helium or Argon Blanks)

I turned off the GC and taken out and put back the TCD signal board. The
spiking went away only on the first run but came back afterward. Also, when the GC has the method on (not on standby), but the run isn't started, spiking still occurs.

The TCD detector is between 7-9 years old. I talked to technical in Agilent and they said either the Filament Cell needs replacement or the signal board.

Is there a post on this forum how to post a image. A very detailed step by step.

tmalew2,

Instructions for posting are in the liquid chromatography section at the top and a post would probably help quite a bit.

What are the flow rates you are using with your TCD, column flow, make-up flow and reference flow? Also, what happens to the signal if you start turning things off, like the TCD heater, the oven heater, the other detector heater.....??

As a matter of curiosity, why did you pull the PDD to switch to a TCD?

Best regards.

By any chance is your signal cable close to a heater cable? I have seen cases where the field from a heater switching off and on have produced spikes in a detector signal when the signal cable was not adequately shielded.