Discroll and Spaziani used photoionization detection (PID) in gas chromatography as early as 1976.A 10.2-eV lamp was employed as the light source for these detectors.Comparison with the flame-ionization detector (FID) revealed that the PID was more sensitive for unsaturated aliphatics and especially for aromatic compounds.Nevertheless, to date neither the PID nor ion-mobility spectrometry (IMS), based on PID development with photoionization, has been widely accepted.The reason may be that with PID, unlike FID, the number of carbon atoms in a hydrocarbon molecule is not proportional to the relative molar response, so that quantitative analysis is rendered more complicated.