Gas Chromatography Detectors - Early Gas Chromatography Detectors > The β-Ray Ionization Detector > Page 25


Hydrogen or a mixture of hydrogen and nitrogen was used as the carrier gas which after passing through the column was burnt at a small jet. A thermocouple was placed above the jet and was heated by the flame. In the presence of a solute, the heat of combustion of the gas increased, raising the flame temperature and the output from the thermocouple. The electronic circuit consisted of a simple backing off circuit to offset the output from the hydrogen flame alone and an attenuating circuit, the output from which passed to a potentiometric recorder. The detector had a linear response over about three orders of magnitude of concentration and a sensitivity of about 1 x 10-6 g/ml (n-heptane). Its response was proportional to the heat of combustion of the solute. This detector was also made commercially but enjoyed a very short life as it was quickly supplanted by the FID.


The b-Ray Ionization Detector Detector


Figure 9 The b-Ray Ionization Detector