Analysis of volatile arsenic compounds formed by intestinal microorganisms: rapid identification of new metabolic products by use of simultaneous EI-MS and ICP-MS detection after gas chromatographic separation

Abstract

For the investigation of biotransformation processes of heteroelements in the environment, both molecular and element-sensitive detection systems are used in hyphenation to chromatographic separation. In this work, we studied the potential of our recently developed gas chromatographic system with parallel electron impact mass spectrometry and inductively coupled plasma mass spectrometry (GC/EI-MS/ICP-MS) for non-target screening and subsequent identification of volatile arsenic compounds formed by fecal microorganisms. By combining the strengths of element-sensitive detection by ICP-MS and molecular identification by EI-MS, it was possible to identify five mixed arsenic/sulfur species (Me₂AsSH, dimethyl-mercapto-arsine, Me₂AsSMe, dimethyl-methylthio-arsine, Me₂AsSSMe, dimethyl-methyldithio-arsine, (Me₂As)₂S, thio-bis(dimethylarsine) and MeAs(SMe)(SEt), methyl-methylthio-ethylthio-arsine) as well as one mixed arsenic/selenium compound (Me₂AsSeMe, dimethyl-methylseleno-arsine) in the headspace of fecal incubations. Identification of all compounds was verified by synthesis experiments. Three of these species, namely Me₂AsSeMe, (Me₂As)₂S and MeAs(SMe)(SEt), have not been described in environmental or human matrices before. Finally, the advantages of elemental and molecular detection after gas chromatographic separation are discussed.