Flame ionization detector effective carbon number

The ionization of carbon compounds in a flame is a poorly understood process, although it has been observed that the number of ions produced is roughly proportional to the number of reduced carbon atoms in the flame. Because the flame ionization detector responds to the number of carbon atoms entering the detector per unit of time, it is a mass-sensitive, rather than a concentration-sensitive, device. As a consequence, this detector has the advantage that changes in flow rate of the mobile phase have little effect on detector respon.se. 

Accurate g.l.c. analysis of mixtures of substances with a flame ionization detector (f.i.d.) depends upon a knowledge of the relative detector response of each compound. Variations in the f.i.d. responses of steroids in molar terms have now been put on a quantitative basis. There is a good linear relationship between molar f.i.d. response and the effective carbon number , which is the number of carbon atoms per molecule less half the number of oxygen atoms (over the ranges Ci8—C31, and Oo—O4). This behaviour parallels earlier conclusions for paraffin hydrocarbons, alcohols, and esters. G.l.c. data are reported for the trimethylsilyl ethers of 49 plant sterols on eight different columns. ... 

Effective Carbon Numbers calculated using Table I, p. 336, of Calculation of Flame Ionization Detector Relative Response Factors Using the Effective Carbon Number Concept by Scanlon and Willis. Journal of Chromatographic Scieiue, Vol 23, August 1985, p. 333-339... 

Jones, F. W., Flame ionization detector relative response factors for oligomers of alkyl and aryl ether polyethoxylates using the effective carbon number concept, 7. Chromatogr. Sci., 1998,56,223-226. 

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