一种新型光电离/微型正交加速飞行时间质谱仪的设计和性能测试

Development and Performance of a Miniature Vacuum Ultraviolet Ionization/Orthogonal Acceleration Time of Flight Mass Spectrometer

介绍了自行研制的光电离/微型正交加速飞行时间质谱仪的设计原理和性能。电离源采用光子能量为10.6 eV真空紫外灯,它可将待测分子电离只产生单电荷母体离子,不产生碎片离子。采用该光电离方法得到的质谱谱图比较简单,气体样品可以不经分离直接进行分析。离子正交引入结构的飞行时间质量分析器有效地提高了质谱分辨率。用32 cm无场飞行管,测量碘甲烷得到的质谱分辨率可达430。在谱图获得频率10 kHz的操作条件下,样品总分析时间20 s,得到苯和碘甲烷的检出限分别为10×10-6,5×10-6。软电离和微型化使得该质谱仪在可挥发性有机物的实时在线监测方面有广泛的应用。

A home-made miniature orthogonal acceleration time of flight mass spectrometer with vacuum uhraviolet （VUV） photoionization source has been designed and tested. The VUV lamp with photon energy 10.5 eV is a soft ionization source to form only parent ion without fragmentation for most organic compounds, which makes the mass spectrum of a mixtures can be identified without prior separation. The orthogonal acceleration structure can improve resolution obviously in a short field free mass analyzer. Resolution of 430 has been achieved in a orthogonal acceleration linear configuration with a 32-cm field free flight path for methyl iodide. The total analysis time is 20 s at the rate of 10 kHz for mass spectra recording, and detection limits of 10 × 10 ^-6（V/V） and 5 × 10^-6（V/V） were measured for benzene and methyl iodide respectrvely. The combination of soft ionization and orthogonal acceleration makes the spectrometer portable and has a wide application in real-time and on-line monitoring of volatile organic compounds.