HYPERTHERMAL SURFACE IONIZATION DETECTOR FOR GAS-CHROMATOGRAPHY

点击翻译按钮获取中文摘要

An experimental study was performed on the influence of the molecular kinetic energy in surface ionization, using Rhenium oxide(ReO_2) or Platinum(Pt) surfaces. Sample molecules were benzene, toluene, o-xylene, and piperidine. They were accelerated to kinetic energies of 5-15 eV by means of seeded supersonic molecular beam method. These accelerated molecules, expanded from a nozzle, were brought to interact with a heated surface by collision, forming positive ions of intact molecules or its fragments.Ionization yield was measured as a function of incident kinetic energy, surface temperature, and system parameters. The ionization yield was increased exponentially above the threshold kinetic energy. This threshold energy was nearly equal to the energy gap phi-IE, werer phi is the work function of the surface and IE is the ionization energy of the organic molecule. The organic molecules were sensitive to the surface temperature, in terms of the ionization efficiency.A home made detector for gas-chromatography with use of this ionization principle was evaluated its function, by comparison with the commercial FID-detector. The evaluated functions were the detection sensitivity, noise level, background level, dynamic range, peak width and the other system parameters. Our detector using Rhenium oxide surface showed excellent detection sensitivity, which was nearly 100 times higher than FID-detector for various kinds of the organic molecules. Noise level and peak width were comparable to those of FID-detector. On the other hand, the dynamic range and the background level stability were poorer than those of FID-detector.