JMSSJ On-line

JMSSJ On-line, Vol. 52 (2004) No. 3, pp. 149-153

Development of an Atmospheric Pressure Penning Ionization Source for Gas Analysis		>> Full Text PDF >> References
*Susumu FUJIMAKI, ^a) Hiroko FURUYA, ^a) Shizuka KAMBARA, ^a) and Kenzo HIRAOKA ^b)** ^a) Graduate School of Engineering, University of Yamanashi (4-3-11 Takeda, Koufu 400-8511, Japan)^b) Clean Energy Research Center, University of Yamanashi (4-3-11 Takeda, Koufu 400-8511, Japan)*

A direct gas introduction type atmospheric pressure Penning ionization source for on-site analysis of environmental organic pollutants was developed. The long-lived metastable argon atoms Ar^* (³P₂ and ³P₀) were utilized for Penning ionization. As the excitation energies of Ar^* are 11.5 eV (³P₂) and 11.8 eV (³P₀), the major components of air such as N₂, O₂, CO₂, CO, and H₂O are not ionized with Ar^* but most of the organic compounds can be ionized. Atmospheric pressure Penning ionization mass spectra of all samples studied in our experiment showed abundant molecular-related ions (M⁺, [M+H]⁺, and [M-H]⁺) as base peaks. In the mass spectra of sample gases (M) mixed with methanol, intense ion [M+CH₃]⁺ was observed in addition to [M+H]⁺ and [2M+H]⁺. The appearance of [M+CH₃]⁺ is due to the occurrence of the methyl cation transfer reaction, CH₃OH₂⁺+M→CH₃⁺M+H₂O.

Key words: Atmospheric pressure Penning ionization, On-site analysis, Methyl cation transfer