Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China.
Anal Chem. 2011 Dec 1;83(23):8992-8. doi: 10.1021/ac201791n. Epub 2011 Nov 3.
A magnetic field enhanced photoelectron ionization (MEPEI) source combined with single photon ionization (SPI) was developed for an orthogonal acceleration time-of-flight mass spectrometer (oaTOFMS). A commercial radio frequency (rf) powered vacuum ultraviolet (VUV) lamp was used as SPI light source, and the photoelectrons generated by photoelectric effect were accelerated to induce electron ionization (EI). The MEPEI was obtained by applying a magnetic field of about 800 G with a permanent annular magnet. Compared to a nonmagnetic field photoelectron ionization source, the signal intensities for SO(2), SF(6), O(2), and N(2) in MEPEI were improved more than 2 orders with the photoelectron energy around 20 eV, while most of the characteristics of soft ionization still remained. Simulation with SIMION showed that the sensitivity enhancement in MEPEI was ascribed to the increase of the electron moving path and the improvement of the electrons transmission. The limits of detection for SO(2) and benzene were 750 and 80 ppbv within a detection time of 4 s, respectively. The advantages of the source, including broad range of ionizable compounds, reduced fragments, and good sensitivity with low energy MEPEI, were demonstrated by monitoring pyrolysis products of polyvinyl chloride (PVC) and the intermediate products in discharging of the SF(6) gas inpurity.
一种与单光子电离（SPI）相结合的磁场增强光电离（MEPEI）源被开发用于正交加速飞行时间质谱仪（oaTOFMS）。商业射频（rf）供电真空紫外线（VUV）灯被用作 SPI 光源，光电效应产生的光电子被加速以诱导电子电离（EI）。通过施加约 800 G 的磁场，使用永磁体获得 MEPEI。与非磁场光电离源相比，在光电能约为 20 eV 时，SO(2)、SF(6)、O(2)和 N(2)在 MEPEI 中的信号强度提高了 2 个数量级以上，而大部分软电离的特性仍然保留。SIMION 模拟表明，MEPEI 中的灵敏度增强归因于电子运动路径的增加和电子传输的改善。在 4 秒的检测时间内，SO(2)和苯的检测限分别为 750 和 80 ppbv。该源的优点包括可电离化合物范围广、碎片减少以及低能 MEPEI 具有良好的灵敏度，通过监测聚氯乙烯（PVC）的热解产物和 SF(6)气体不纯放电过程中的中间产物得到了证明。
