title: New method and detection of high concentrations of monomethylarsonous acid detected in contaminated groundwater.
abstract: Monomethylarsonous acid (MMAIII) was detected in groundwater from a former herbicide production plant in the USA. The site has total arsenic concentrations up to thousands of mg/L, representing one of the most severe cases of arsenic contamination ever reported. Structure-specific detection of MMAIII, along with arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMAV), and dimethylarsinic acid (DMAV), was achieved using liquid chromatography separation with electrospray ionization tandem mass spectrometry detection (HPLC-ESI-MS/MS). To enable the electrospray of MMAIII and AsIII, dimercaptosuccinic acid (DMSA) was used to derivatize these trivalent arsenicals online, so that their complexes with DMSA could be detected using negative ionization ESI-MS/MS. The presence of MMAIII was verified using high resolution mass spectrometry to measure accurate mass, tandem mass spectrometry to monitor fragmentation, and three different separation techniques to resolve arsenic species. The measured accurate mass of the suspected MMAIII compound in a groundwater sample was 122.9607+/-0.0003 amu, which was in good agreement with the theoretical value and that of the MMAIII standard. Simultaneous monitoring of AsO+ at m/z 91 and SO+ at m/z 48 using HPLC-ICPMS operating in dynamic reaction cell mode ruled out possible confounding from any sulfur-containing arsenic compound. The concentrations of MMAIII found in the groundwater samples from a contaminated site were as high as 3.9-274 mg/L, the highest ever observed in the environment.
authors.affiliation: Department of Chemistry, University of Alberta, 10-102 Clinical Sciences Building, Edmonton, Alberta, Canada T6G 2G3.
authors.forename: Anthony
authors.initials: A
authors.lastname: McKnight-Whitford
authors.forename: Baowei
authors.initials: B
authors.lastname: Chen
authors.forename: Hua
authors.initials: H
authors.lastname: Naranmandura
authors.forename: Chen
authors.initials: C
authors.lastname: Zhu
authors.forename: X Chris
authors.initials: XC
authors.lastname: Le
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry*; D006540:Herbicides / Q000032:analysis* / Q000737:chemistry; D009942:Organometallic Compounds / Q000032:analysis* / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D006540:Herbicides; D009942:Organometallic Compounds; D014874:Water Pollutants, Chemical; C406082:monomethylarsonous acid