Thermal Conductivity Detector

Introduction Thermal conductivity detectors have been in use since before the beginning of gas chromatography. Compares the thermal conductivity of two gas flows – the pure carrier (reference) gas and the sample..

Uses Thermal Conductivity Detector used to analyses inorganic gases (Argon, Nitrogen, Hydrogen, Carbon Dioxide, etc) and small hydrocarbon molecules.

Detector component

Detector component Tow cells with small volume termed as: Reference cell Sample cell Each cell has a resistance wire or thermistor or filament that posses a high temperature co efficient or resistance.

Principle

Principle The sample components in the carrier gas pass into the measuring channel. A second channel serve as a reference channel where the pure carrier gas flows. Electrically heated resistance wire are located into both channels.

Principle The difference in thermal conductivity between the column effluent flow(sample components in the carrier gas ) and the reference flow of carrier alone, produces a voltage signal difference proportional to this difference. This signal is proportional to the concentration of sample components.

Sensitivity The sensitivity of TCD response to various solutes is dictated by the solutes' thermal conductivities relative to the carrier. This makes TCD respond universally without dependence upon specific chemical elements or structures.

Advantages Ease and simplicity of use. Broad application to inorganic and organic compounds. Its nondestructive character, which permits collection of solutes after detection.

Disadvantages The chief limitation of the thermal conductivity detector is its relatively low sensitivity.

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