A hydrogen-conversion detector for gas chromatography.

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THE thermal conductivity cell is in common use as a detector in gas chromatography. When separating high-boiling compounds it is necessary to heat the cell to avoid condensation effects, but with nitrogen as the mobile phase this results in loss of sensitivity. The use of hydrogen or helium instead of nitrogen is said to improve sensitivity but apparently gives broader peaks and less resolving power1,2. Using nitrogen as the carrier gas, Martin and Smart3 obtained improved sensitivity by converting the compounds as they emerged from the column into carbon dioxide and water, and detecting the carbon dioxide by an infra-red gas analyser. In this laboratory this technique has been tried using a thermal conductivity cell to detect the carbon dioxide after removal of water vapour. In our experience this method gives increased sensitivity but is accompanied by some band spreading and consequent loss of resolution.