title: LC/QTOF-MS fragmentation of N-nitrosodimethylamine precursors in drinking water supplies is predictable and aids their identification.
abstract: N-Nitrosodimethylamine (NDMA) is carcinogenic in rodents and occurs in chloraminated drinking water and wastewater effluents. NDMA forms via reactions between chloramines and mostly unidentified, N-containing organic matter. We developed a mass spectrometry technique to identify NDMA precursors by analyzing 25 model compounds with LC/QTOF-MS. We searched isolates of 11 drinking water sources and 1 wastewater using a custom MATLAB®program and extracted ion chromatograms for two fragmentation patterns that were specific to the model compounds. Once a diagnostic fragment was discovered, we conducted MS/MS during a subsequent injection to confirm the precursor ion. Using non-target searches and two diagnostic fragmentation patterns, we discovered 158 potential NDMA precursors. Of these, 16 were identified using accurate mass combined with fragment and retention time matches of analytical standards when available. Five of these sixteen NDMA precursors were previously unidentified in the literature, three of which were metabolites of pharmaceuticals. Except methadone, the newly identified precursors all had NDMA molar yields of less than 5%, indicating that NDMA formation could be additive from multiple compounds, each with low yield. We demonstrate that the method is applicable to other disinfection by-product precursors by predicting and verifying the fragmentation patterns for one nitrosodiethylamine precursor.
authors.affiliation: Department of Civil and Environmental Engineering, University of Nevada, Reno, NV 89557-0258, United States. Electronic address: DHanigan@asu.edu.
authors.forename: David
authors.initials: D
authors.lastname: Hanigan
authors.affiliation: Center for Environmental Mass Spectrometry, Department of Environmental Engineering, University of Colorado at Boulder, Boulder, CO 80303, United States.
authors.forename: Imma
authors.initials: I
authors.lastname: Ferrer
authors.affiliation: Center for Environmental Mass Spectrometry, Department of Environmental Engineering, University of Colorado at Boulder, Boulder, CO 80303, United States.
authors.forename: E Michael
authors.initials: EM
authors.lastname: Thurman
authors.affiliation: School of Molecular Sciences, Arizona State University, Tempe, AZ 85287-1604, United States.
authors.forename: Pierre
authors.initials: P
authors.lastname: Herckes
authors.affiliation: School of Sustainable Engineering and the Built Environment, Arizona State University, Box 3005, Tempe, AZ 85287-3005, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Westerhoff
mesh_terms: D005591:Chemical Fractionation / Q000295:instrumentation / Q000379:methods*; D002853:Chromatography, Liquid; D004128:Dimethylnitrosamine / Q000032:analysis*; D060766:Drinking Water / Q000032:analysis*; D013058:Mass Spectrometry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000592:standards*
chemical_list: D060766:Drinking Water; D014874:Water Pollutants, Chemical; D004128:Dimethylnitrosamine
keywords: Diagnostic ion; Disinfection by-product; N-Nitrosodimethylamine; Precursor; Time-of-flight