Thermal conductivity (TCD) is a commonly used detector in gas chromatography. TCD works by having two parallel tubes both containing gas and heating coils. The gases are examined by comparing the heat loss rate from the heating coils into the gas. Normally one tube holds a reference gas and the sample to be tested is passed through the other. Using this principle, a TCD senses the changes in the thermal conductivity of the column effluent and compares it to a reference flow of carrier gas. Most compounds have a thermal conductivity much less than that of the common carrier gases of hydrogen or helium. Therefore, when an analyte elutes from the column, the thermal conductivity of the effluent is reduced and a detectable signal is produced. Helium has traditionally been the favoured carrier gas but as laboratory trends change, Linde is also able to offer hydrogen as an alternative to helium as a carrier gas for GC-TCD applications.
While flame ionization detector (FID) can provide very good resolution, TCD is a good general purpose detector for initial investigations with an unknown sample, as it responds to all compounds, thanks to the fact that all compounds, organic and inorganic, have a different thermal conductivity from helium. The TCD is also used in the analysis of permanent and inorganic gases (for example argon, oxygen, nitrogen, carbon dioxide, carbon monoxide, sulfur dioxide) because it responds to all these substances unlike the FID, which cannot detect compounds which do not contain carbon-hydrogen bonds.
Gas Chromatograph with Thermal Conductivity Detector (GC - TCD)
Detection Limit |
Recommended Gas |
Recommended Cylinder Regulator |
≤ 100 ppm |
HiQ Calibration Mixures | BASELINE C106 series |
≤ 1 ppm | HiQ Calibration Mixures | REDLINE C200 series |
Detection Limit |
Recommended Gas |
Recommended Cylinder Regulator |
Recommended Gas Generator |
≤ 100 ppm |
HiQ Helium 5.0 | BASELINE C106 series | n/a |
≤ 100 ppm |
HiQ Hydrogen 5.0 | BASELINE C106 series | HiQ PGH2 Hydrogen |
≤ 100 ppm |
HiQ Nitrogen 5.0 | BASELINE C106 series | HiQ HPN2 Nitrogen |
≤ 1 ppm |
HiQ Helium 6.0 | REDLINE C200 series | n/a |
≤ 1 ppm |
HiQ Hydrogen 6.0 | REDLINE C200 series | HiQ NMH2 Hydrogen |
≤ 1 ppm |
HiQ Nitrogen 6.0 | REDLINE C200 series | n/a |
Detection Limit |
Recommended Gas |
Recommended Cylinder Regulator |
Recommended Gas Generator |
≤ 100 ppm |
HiQ Argon 5.0 | BASELINE C106 series | n/a |
≤ 100 ppm |
HiQ Helium 5.0 | BASELINE C106 series | n/a |
≤ 100 ppm |
HiQ Hydrogen 5.0 | BASELINE C106 series | HiQ PGH2 Hydrogen |
≤ 100 ppm |
HiQ Nitrogen 5.0 | BASELINE C106 series | HiQ HPN2 Nitrogen |
≤ 1 ppm |
HiQ Argon 6.0 | REDLINE C200 series | n/a |
≤ 1 ppm |
HiQ Helium 6.0 | REDLINE C200 series | n/a |
≤ 1 ppm |
HiQ Hydrogen 6.0 | REDLINE C200 series | HiQ PGH2 Hydrogen |
≤ 1 ppm |
HiQ Nitrogen 6.0 | REDLINE C200 series | n/a |
Detection Limit |
Recommended Gas |
Recommended Cylinder Regulator |
Recommended Gas Generator |
≤ 100 ppm |
HiQ Helium 5.0 | BASELINE C106 series | n/a |
≤ 100 ppm |
HiQ Hydrogen 5.0 | BASELINE C106 series | HiQ PGH2 Hydrogen |
≤ 100 ppm |
HiQ Nitrogen 5.0 | BASELINE C106 series | HiQ HPN2 Nitrogen |
≤ 1 ppm |
HiQ Helium 6.0 | REDLINE C200 series | n/a |
≤ 1 ppm |
HiQ Hydrogen 6.0 | REDLINE C200 series | HiQ NMH2 Hydrogen |
≤ 1 ppm |
HiQ Nitrogen 6.0 | REDLINE C200 series | n/a |