National Engineering Laboratory for VOCs Pollution Control Material & Technology, University of Chinese Academy of Sciences, Beijing, 101408, China.
National Engineering Laboratory for VOCs Pollution Control Material & Technology, University of Chinese Academy of Sciences, Beijing, 101408, China.
Talanta. 2022 Sep 1;247:123558. doi: 10.1016/j.talanta.2022.123558. Epub 2022 May 17.
Single-photon ionization mass spectrometry (SPI-MS) is an attractive analytical technique for the online detection of volatile organic compounds; however, the low photon flux of the vacuum ultraviolet (VUV) lamp commonly used in the SPI ion source and the corresponding low detection sensitivity remain a constraint to its wide field applications. In this study, a new VUV lamp-based SPI ion source was developed. By increasing the discharging volume and optimizing the configuration of the lens and ionizer, the photon flux of the VUV lamp and the sensitivity of the ion source were significantly improved. The VUV lamp output was 2.8 × 10 photons s, which was focused into the small ionization zone, and the ion intensity of gaseous benzene under SPI achieved 1.7 × 10 counts per second per pptv (cps pptv). This ion source can also function in photoinduced associative ionization (PAI) mode by introducing gaseous CHCl to initiate an associative ionization reaction. Because of the high efficiency of the ion source, the amount of doped CHCl needed for PAI was greatly reduced (∼2.5% of that used in previous experiments). PAI exhibited an outstanding protonation effect on monosulfur ethers (CHS). The signal intensities of the protonated molecular ions (MH) were 46-128 times higher than those of the molecular ions (M) produced by SPI. Since monosulfur ethers generally have lower SPI cross-sections than polysulfur ethers (CHS or CHS), the PAI and SPI modes were selected for the online measurement of a series of mono- and polysulfur ethers, respectively. The obtained detection sensitivity of the mono- and polysulfur ethers reached 476.5 ± 1.72-2835.1 ± 99.5 and 47.9 ± 0.4-105.1 ± 2.3 counts pptv, respectively, in 10 s of sampling time. The corresponding 3σ limits of detection (LODs) were 0.12-0.71 and 0.06-0.14 pptv, respectively. This study provides advances in the development of a high-flux VUV lamp and a highly efficient SPI/PAI ion source, as well as an ultrasensitive analytical method for detecting sulfur ethers.
单光子电离质谱（SPI-MS）是一种很有吸引力的分析技术，可用于在线检测挥发性有机化合物；然而，SPI 离子源中常用的真空紫外（VUV）灯的低光子通量以及相应的低检测灵敏度仍然限制了其广泛应用。在本研究中，开发了一种基于新型 VUV 灯的 SPI 离子源。通过增加放电体积并优化透镜和离子化器的配置，VUV 灯的光子通量和离子源的灵敏度得到了显著提高。VUV 灯的输出为 2.8×10 个光子 s，被聚焦到小的电离区，SPI 下气态苯的离子强度达到 1.7×10 个每 pptv 每秒计数（cps pptv）。该离子源还可以通过引入气态 CHCl 来启动缔合电离反应，在光诱导缔合电离（PAI）模式下工作。由于离子源效率高，PAI 所需的掺杂 CHCl 量大大减少（约为之前实验用量的 2.5%）。PAI 对单硫醚（CHS）表现出出色的质子化作用。质子化分子离子（MH）的信号强度比 SPI 产生的分子离子（M）高 46-128 倍。由于单硫醚的 SPI 截面通常低于多硫醚（CHS 或 CHS），因此选择 PAI 和 SPI 模式分别用于一系列单硫醚和多硫醚的在线测量。获得的单硫醚和多硫醚检测灵敏度分别达到在 10 s 的采样时间内，476.5±1.72-2835.1±99.5 和 47.9±0.4-105.1±2.3 counts pptv，相应的 3σ 检出限（LOD）分别为 0.12-0.71 和 0.06-0.14 pptv。本研究在开发高通量 VUV 灯和高效 SPI/PAI 离子源方面取得了进展，以及开发了一种用于检测硫醚的超灵敏分析方法。
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