Single Photon Ionization and Chemical Ionization Combined Ion Source Based on a Vacuum Ultraviolet Lamp for Orthogonal Acceleration Time-of-Flight Mass Spectrometry

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• 作者：Lei Hua ; Qinghao Wu ; Keyong Hou ; Huapeng Cui ; Ping Chen ; Weiguo Wang ; Jinghua Li ; Haiyang Li
• 刊名：Analytical Chemistry
• 出版年：2011
• 出版时间：July 1, 2011
• 年：2011
• 卷：83
• 期：13
• 页码：5309-5316
• 全文大小：957K
• 年卷期：v.83,no.13(July 1, 2011)
• ISSN：1520-6882

文摘

A novel combined ion source based on a vacuum ultraviolet (VUV) lamp with both single photon ionization (SPI) and chemical ionization (CI) capabilities has been developed for an orthogonal acceleration time-of-flight mass spectrometer (oaTOFMS). The SPI was accomplished using a commercial 10.6 eV krypton discharge lamp with a photon flux of about 10¹¹ photons s^鈥?, while the CI was achieved through ion鈥搈olecule reactions with O₂⁺ reactant ions generated by photoelectron ionization at medium vacuum pressure (MVP). To achieve high ionization efficiency, the ion source pressure was elevated to 0.3 mbar and the photoionization length was extended to 36 mm. As a result, limits of detection (LODs) down to 3, 4, and 6 ppbv were obtained for benzene, toluene, and p-xylene in MVP-SPI mode, and values of 8 and 10 ppbv were obtained for toluene and chloroform, respectively, in SPI-CI mode. As it is feasible to switch between MVP-SPI mode and SPI-CI mode rapidly, this system is capable of monitoring complex organic mixtures with a wide range of ionization energies (IEs). The analytical capacity of this system was demonstrated by measuring dehydrogenation products of long-chain paraffins to olefins through direct capillary sampling and drinking water disinfection byproducts from chlorine through a membrane interface.