About as sensitive
as a TCD, the Catalytic Combustion Detector has
the hydrocarbon selectivity of an FID, plus the
ability to operate on air alone. Because the CCD requires no compressed
gases like hydrogen or helium, it can be used in SRI's Gasless
GCs where our internal "whisper quiet"
air compressor supplies the ambient air carrier gas. The CCD detector
can also be used as a hydrocarbon monitor in non-chromatographic applications
where the CCD senses the total hydrocarbon content of a flowing air stream,
or as a hydrogen/hydrocarbon leak detector.
The CCD sensor, shown
above, is rugged and can be expected to last a long time. A second sensor
is included in the detector housing at no extra cost, providing a built-in
replacement should the first sensor become inoperable. Replacement sensor
sets install in minutes without tools and are very economical, making
this detector a good choice for academic settings where the sensors may
be damaged by inexperienced operators.
Our CCD detector consists
of a tiny coil of platinum wire embedded in a catalytic ceramic bead.
A small electric current flows through the patinum coil, heating the ceramic
bead to around 500oC. The CCD is maintained in an oxidative
environment by using air carrier gas. When a hydrogen or hydrocarbon molecule
impacts the hot bead, it combusts on the surface and raises the temperature
and resistance of the platinum wire. This resistance change causes the
detector output signal to change, thus producing a peak. The brass detector
housing is mounted on a stainless steel bulkhead fitting, which is mounted
directly in the wall of the GC column oven.