Aspects of the mechanism of the flame ionization detector

The development of flame ionization detection took place on an empirical basis without a clear understanding of the mechanism. The study of flames by mass spectrometry showed that the all-important ion was the formylium ion CHO+. The pre-combustion degradation was thought to be a pyrolytic degradation and hydrogenation at the high temperatures obtained close to the combustion zone. Using a capillary probe inside the flame it was recently shown that a degradation of all hydrocarbons to methane takes place at low temperatures by the reaction of hydrogen atoms which are generated in the burning hydrogen. The effects of heteroatoms and of H-2 substitution was studied by the same method. (C) 1999 Elsevier Science B.V. All rights reserved.