Thermionic detector for gas chromatography

TLDR: In this article, the authors used bucking voltage to oppose the effect of ions produced in the presence of organic components containing phosphorus or a halogen, which increased the rate of ionization of material from the ion source block.

Abstract: 1,160,828. Gas analysis. VARIAN ASSOCIATES. June 1, 1967 [June 6, 1966], No.25410/67. Heading G1N. Effluent gas from a chromatographic column is mixed with hydrogen and the mixture is burnt in air at the upper surface of a homogeneous ion source block 29 so that the heat of the resulting flame can ionize material from the surface of the ion source to introduce charged particles into the space between electrodes 32, 34. The ion source block 29 preferably consists of a salt of an alkali, or alkaline earth, metal (examples given) containing 2 to 5% refractory binder, e.g. silica. In the presence of an organic constituent containing phosphorus or a halogen, the rate of ionization of material from the ion source block is increased. The relative sensitivity to phosphorus and halogens depends on the air and hydrogen input flow rates so that by proper adjustment of the flow rates, the detector can be made virtually insensitive to halogens, responding only to phosphorus. A bucking voltage is used to oppose the effect of ions produced in the absence of phosphorus or a halogen. Electrode 32 also serves as an ignition coil.