SRI TCD DETECTOR
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Universal detector |
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Detects 200ppm to
100% |
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Easily replaceable
filaments |
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Thermostatted to
275°C |
The SRI TCD
detector consists of four tungsten-rhenium
filaments in a Wheatstone bridge configuration.
Electric current flows through the four
filaments causing them to heat up. Carrier gas (
typically helium which has very high thermal
conductivity ) flows across the filaments
removing heat at a constant rate. When a sample
molecule with lower thermal conductivity exits
the column and flows across the two sample
filaments, the temperature of the filaments
increases unbalancing the Wheatstone bridge and
generating a peak as the sample molecules
transit through the detector.
The TCD
detector is useful because it detects all
molecules, not just hydrocarbons, so it is
commonly used for fixed gas analysis ( O2, N2,
CO, CO2, H2S, NO, NO2, etc. ) where the target
analytes do not respond well on other more
sensitive detectors. |
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The TCD is able to detect concentrations from
100% down to about 100 ppm, but not lower. Even
100 ppm is only possible where the
chromatography permits a sharp peak on a flat
baseline. Where the peak is broad or the
baseline is not perfectly flat, detection limits
of 300 ppm are more realistic. For lower
detection limits, the HID detector may be more
suitable for inorganics, and of course the FID
provides 1 ppm detection for hydrocarbon
species.
The SRI TCDs
use easily replaceable filaments which allow
user replacement in the event of a filament
burn-out. A filament protection circuit prevents
filament damage by disabling the current if
carrier gas pressure is not detected at the GC,
but cannot prevent filament damage under all
circumstances.
Click here
for printable TCD technical overview (.pdf).
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#SRI-8690-0007,
TCD DETECTOR |
$2,059.00 |
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