44
GCDetectors
CCD -CatalyticCombustionDetector
• DetectsDown to 500ppm
• HydrocarbonandHydrogenSelective
• GaslessOperatingCapability
• InexpensiveandRugged
• Built-inSpare!
This chromatogramshows
a separation of 1000ppm
methanol fromacetoneusing
a1meterHayeSep-Dpacked
column at 150
o
C and air
carrier from the GC’s built-
in air compressor. The
negative peak at the
beginningof theruniswater.
TheCCDhousing is about 1cmindiameter. Inside,
there are 2 sensor elements consistingof a platinum
wire embedded in a catalytic ceramicbead.
Sensor
elements
(enlarged)
The CCD is about as sensitive as a TCD, but it has
the hydrocarbon selectivity of an FID while capable
of operating on air alone. Because the CCD needs no
compressed gases like hydrogen or helium, it can be
used in SRI’s Gas-less
TM
GCs where a built-in, “whisper
quiet”air compressor supplies theambient air carrier gas.
TheCCD can also be used as a hydrocarbonmonitor in nonchromatographic applicationswhere theCCD
senses the total hydrocarbon content of a lowing air stream, or as a hydrogen/hydrocarbon leakdetector.
TheCCD detector sensor 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 irst 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 detector may be damaged by inexperienced
operators.
TheCatalyticCombustionDetector consists of a tiny coil of platinumwire embedded in a catalytic ceramic
bead. A small electric current lows through the platinum coil, heating the ceramic bead to around 500°C.
The CCD ismaintained in an oxidative environment typically by using air carrier gas. When a hydrogen or
hydrocarbonmolecule impacts the hot bead, it combusts on the surface and raises the temperature and
resistance of the platinumwire. 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 itting, which is
secureddirectly to thewall of theGC columnoven.
8690-2007
CCDdetector
8670-2007
Replacement CCDdetector housing (2 sensors in1housing)
