Photoionization-Generated Dibromomethane Cation Chemical Ionization Source for Time-of-Flight Mass Spectrometry and Its Application on Sensitive Detection of Volatile Sulfur Compounds

详细信息    查看全文

• 作者：Jichun Jiang ; Yan Wang ; Keyong Hou ; Lei Hua ; Ping Chen ; Wei Liu ; Yuanyuan Xie ; Haiyang Li
• 刊名：Analytical Chemistry
• 出版年：2016
• 出版时间：May 17, 2016
• 年：2016
• 卷：88
• 期：10
• 页码：5028-5032
• 全文大小：362K
• 年卷期：0
• ISSN：1520-6882

文摘

Soft ionization mass spectrometry is one of the key techniques for rapid detection of trace volatile organic compounds. In this work, a novel photoionization-generated dibromomethane cation chemical ionization (PDCI) source has been developed for time-of-flight mass spectrometry (TOFMS). Using a commercial VUV lamp, a stable flux of CH₂Br₂⁺ was generated with 1000 ppmv dibromomethane (CH₂Br₂) as the reagent gas, and the analytes were further ionized by reaction with CH₂Br₂⁺ cation via charge transfer and ion association. Five typical volatile sulfur compounds (VSCs) were chosen to evaluate the performance of the new ion source. The limits of detection (LOD), 0.01 ppbv for dimethyl sulfide and allyl methyl sulfide, 0.05 ppbv for carbon disulfide and methanthiol, and 0.2 ppbv for hydrogen sulfide were obtained. Compared to direct single photon ionization (SPI), the PDCI has two distinctive advantages: first, the signal intensities were greatly enhanced, for example more than 10-fold for CH₃SH and CS₂; second, H₂S could be measured in PDCI by formation [H₂S + CH₂Br₂]⁺ adduct ion and easy to recognize. Moreover, the rapid analytical capacity of this ion source was demonstrated by analysis of trace VSCs in breath gases of healthy volunteers and sewer gases.