Windowless pulsed-discharge photoionization detector - Application to qualitative analysis of volatile organic compounds

The effluent from a gas chromatograph was split and directed to four identical windowless photoionization detectors. These detectors use pure helium, helium with Ar (0.64%), Ar (4.15%) and Kr (0.58%) as the discharge gas. The relative ionization cross-sections can be obtained from the ratio of the normalized response using an internal standard. This value is characteristic of the compound and could be used for qualitative analysis. These ratios for 47 compounds encompassing 13 functional groups have been determined and are reported. The values have an average relative standard deviation of 2% for the majority of the compounds. The long-term reproducibility of a smaller set of compounds has been determined and was 0.78-2% relative standard deviation for the Ar detector and 5.6-11.3% (worse cases) where the response of the krypton detector is low.