Characterization of Unknown Brominated Disinfection Byproducts during Chlorination Using Ultrahigh Resolution Mass Spectrometry

Haifeng Zhang,^† Yahe Zhang,^‡ Quan Shi,^‡ Hongdie Zheng,^†,§ and Min Yang^†,*

^†State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 

^‡State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China 

^§College of Geosciences, China University of Petroleum, Beijing 102249, China

^*Corresponding Author: Phone: +86-10-62923475; fax: +86-10-62923541; e-mail: yangmin@rcees.ac.cn.

DOI: 10.1021/es4057399

Keywords: Drinking Water; Fragmentation; Halogenation; Ions; Molecular Structure

Abstract: Brominated disinfection byproducts (Br-DBPs), formed from the reaction of disinfectant(s) with natural organic matter in the presence of bromide in raw water, are generally more cytotoxic and genotoxic than their chlorinated analogues. To date, only a few Br-DBPs in drinking water have been identified, while a significant portion of Br-DBPs in drinking water is still unknown. In this study, negative ion electrospray ionization ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was used to characterize unknown Br-DBPs in artificial drinking water. In total, 441 formulas for one-bromine-containing products and 37 formulas for two-bromine-containing products, most of which had not been previously reported, were detected in the chlorinated sample. Most Br-DBPs have corresponding chlorine-containing analogues with identical CHO composition. In addition, on-resonance collision-induced dissociation (CID) of single ultrahigh resolved bromine containing mass peaks was performed in the ICR cell to isolate single bromine-containing components in a very complex natural organic matter spectrum and provide structure information. Relatively abundant neutral loss of CO₂ was observed in MS−MS spectra, indicating that the unknown Br-DBPs are rich in carboxyl groups. The results demonstrate that the ESI FT-ICR MS method could provide valuable molecular composition and structure information on unknown Br-DBPs.