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

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 collisioninduced 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 CO 2 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. ■ INTRODUCTIONDuring disinfection treatment of drinking water, naturally occurring bromide present in source water can be rapidly oxidized by chlorine to hypobromous acid (HOBr), which has been noted to be more powerful in reacting with natural organic matter (NOM) to form disinfection byproducts (DBPs) than hypochlorous acid (HOCl). 1−3 Toxicological studies have shown that brominated DBPs (Br-DBPs) are generally more cytotoxic and genotoxic than their chlorinated analogues. 4−7 For example, bacterial studies have shown that bromoacetic acid is approximately 20 times more cytotoxic and 200 times more mutagenic in Salmonella typhimurium strain TA100 than chloroacetic acid. 6 Mammalian cell studies have shown that bromoacetic acid is 90 times more cytotoxic and 25 times more genotoxic in Chinese hamster ovary cells than chloroacetic acid. 6 Identifying and controlling Br-DBPs have thus been important issues in securing drinking water safety.To date, approximately 110 Br-DBPs have been reported as drinking water DBPs, most of which were identified by gas chromatography/mass spectrometry (GC−MS) with or without derivatization. 6,8−10 Even with derivatization, however, GC−MS generally is not amenable to the detection of polar/ highly polar Br-DBPs. Zhang et al. 11 have recently developed the precursor ion scan (PIS) method using electrospray ionization-triple quadrupole mass spectrometry (ESI-tqMS) for fast selective detection of polar/highly polar Br-DBPs. In this method, precursor ion scans of m/z 79 and 81 were used to selectively detect the Br-DBPs, and product ion scan...

Characterization of unknown iodinated disinfection byproducts during chlorination/chloramination using ultrahigh resolution mass spectrometry

“…The FT-ICR mass spectrometer was externally calibrated for a mass range of 150-800 using a sodium formate aqueous solution (Zhang et al, 2012a;Zhang et al, 2014). The acquired spectra were internally recalibrated with a known homologous series of the SRFA sample (Zhang et al, 2012a;Zhang et al, 2014).…”

“…The acquired spectra were internally recalibrated with a known homologous series of the SRFA sample (Zhang et al, 2012a;Zhang et al, 2014). After internal calibration, mass accuracy of b 1 ppm was achieved.…”

“…In this study, solid phase extraction (SPE) was used to extract complex mixtures of DBPs, as pointed in previous studies (Zhang et al, 2012a;Zhang et al, 2014), only C18 extractable DBP molecules were analyzed by mass spectrometry. In addition, the mass range was set to m/z 150-800.…”

“…However, recent studies have shown that a significant portion of unknown halogen containing DBPs would be polar/highly polar (Zhang et al, 2008;Ding and Zhang, 2009;Zhang et al, 2012a;Zhang et al, 2014). Ding and Zhang (2009) have successfully identified 17 polar/highly polar I-DBPs using the precursor ion scan (PIS) method via electrospray ionization-triple quadrupole mass spectrometry (ESI-tqMS).…”

“…However, the unit mass resolution of tqMS is still too low to allow nominally isobaric ions to be massresolved and may bias the compositional interpretation of I-DBPs. Recently, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been successfully used to characterize the previously unknown Cl-DBPs and Br-DBPs (Zhang et al, 2012a;Zhang et al, 2012b;Lavonen et al, 2013;Zhang et al, 2014). The ultrahigh resolution and mass accuracy of FT-ICR MS combined with electrospray ionization (ESI) allows the determination of unambiguous and exact molecular formulas (Stenson et al, 2003;Kim et al, 2006aKim et al, , 2006bHertkorn et al, 2008).…”