Analytical Sciences

Deoxidation of Fenthion Sulfoxide, Fenthion Oxon Sulfoxide and Fensulfothion in Gas Chromatograph/Mass Spectrometer, and the Prevention of Sulfoxide Deoxidation by Polyethylene Glycol 300

Kuniyo SUGITATE,*1,*2 Takashi YAMAGAMI,*3,*4 Sadao NAKAMURA,*1 Akira TORIBA,*2 and Kazuichi HAYAKAWA*2

*1 Agilent Technologies Japan, Ltd., 9-1 Takakura-cho, Hachioji, Tokyo 192-8510, Japan
*2 Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan
*3 Nishikawa Keisoku Co., Ltd., YBP West Tower 2F, 134 Godo-cho, Hodogaya, Yokohama, Kanagawa 240-0005, Japan
*4 The University of Kitakyushu, 1-1 Hibikino, Wakamatsu, Kitakyushu, Fukuoka 808-0135, Japan

Fenthion, fenthion sulfoxide, fenthion oxon sulfoxide and fensulfothion showed two different mass spectra in GC/MS, depending on their concentrations. The base peaks shifted to lower levels by 1 m/z at lower concentration, and no retention time shifts were observed. The “shifted base peaks” were not obtained by a general EI fragmentation. The product ion scan spectra of the “shifted base peaks” were coincident with those of molecular ions of their corresponding sulfides. These phenomena can be ascribed to the conversion of sulfoxide into sulfide by the dominant deoxidation reaction than EI fragmentation in an ion source. Adding polyethylene glycol 300 (PEG300) into a test solution prevented sulfoxide deoxidation.

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