By stef on Thursday, May 6, 1999 - 01:20 am:

I'm a student from Belgium who's working with a GC. This GC uses a micro Thermal Conductivity Detector (TCD).
Does anyone know what it is? How it works? What it looks like?

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By Anonymous on Friday, May 7, 1999 - 02:11 pm:

Sure, a thermal conductivity detector is a universal detector (responds to everything), but not necessarily very sensitive. It is based on a Wheatstone bridge, where the sample gas passes over one resistance element and a reference gas over another. The difference in thermal conductivity changes the resistance in the circuit and it becomes imbalanced. This imbalance is converted to a signal to the recording device. The detector can give either positive or negative peaks depending on the relative thermal conductivity of the sample stream vs the reference stream.