Dependence of Mass Spectrometric Fragmentation on the Bromine Substitution Pattern of Polybrominated Diphenyl Ethers

Abstract

This study investigates the link between the bromine substitution and the mass spectrometric fragmentation of polybrominated diphenyl ethers (PBDEs). The mass spectra of 180 PBDEs were obtained in both electron impact (EI) and electron capture negative ionization (ECNI) modes using a single quadrupole mass spectrometer (MS) as well as EI using a tandem MS (MS/MS). The major ions are M(+), [M-2Br](+), [M-2Br](2+) and [M-nBr-28](+) in EI, and Br(-), [HBr2](-) and [C6BrnO](-) in ECNI. In EI-MS, congeners without ortho bromine or having 2,3 substitution on one ring and no ortho bromines on the other were more robust than the others in each homolog. These congeners generated low [M-2Br](+) but relatively high [M-2Br](2+) in EI-MS and negligible [HBr2](-) in ECNI-MS. In EI-MS/MS, the molecular ions of these congeners required higher collision energy to debrominate, and produced additional ions of [M-nBr](+) and [M-nBr-28](+). Full ortho substitution promotes C-O cleavage forming [C6BrnO](-) in ECNI for congeners with >5 bromines. The relationship between the abundance of M(+) and collision energy of the EI-MS/MS was well characterized with a logistic regression model. Principle component analysis found associations between the inflection point collision energy and a few molecular descriptors. Quantum chemistry simulations revealed different EI-induced fragmentation mechanisms among four dibrominated congeners, supporting the hypothesized formation of a stable dibenzofuran-like intermediate during the fragmentation of some congeners but not of others.

Polyhalogenated Carbazoles in Sediments of Lake Michigan: A New Discovery

“…24 PBDE congeners can also produce doubly charged ions of [M−2Br] 2+ upon EI ionization, particularly for those with no ortho bromine or having 2,3-substitution on one ring and no ortho bromines on the other. 25 The formation of a dibenzofuran-like fragment ion during EI ionization of PBDEs was proposed. 26 In the present study, the doubly charged ion [M] 2+ observed in the EI spectra of halogenated carbazoles may reflect their structural similarity to halogenated dibenzofurans.…”

Simple Pretreatment for the Analysis of Additives and Polymers by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Using a Through-Hole Alumina Membrane as a Functional Substrate

“…In the DIUTHAME mass spectrum (Figure a), strong peaks around m / z 486 are predominantly observed and identified as C 6 Br 5 O – by comparing the pattern to the theoretical isotope distribution. It is a representative fragment of DBDE in negative-ion mode. , In the MALDI mass spectrum (Figure b), C 6 Br 5 O – is also observed with no intact DBDE but together with strong peaks of matrix clusters. It is difficult to prevent this interference of matrix cluster ions, regardless of the matrix.…”

“…It becomes even more severe when analyzing low concentrations of DBDE as described below. C 6 Br 5 O – ions can also be generated from nona-BDEs (BDE-207 and BDE-208) and octa-BDE (BDE-204) . This absence of discrimination is not detrimental to rapid screening, since these homologs are also comprehensively banned.…”

“…It is a representative fragment of DBDE in negative-ion mode. 35,36 In the MALDI mass spectrum (Figure 3b), C 6 Br 5 O − is also observed with no intact DBDE but together with strong peaks of matrix clusters. It is difficult to prevent this interference of matrix cluster ions, regardless of the matrix.…”

“…C 6 Br 5 O − ions can also be generated from nona-BDEs (BDE-207 and BDE-208) and octa-BDE (BDE-204). 36 This absence of discrimination is not detrimental to rapid screening, since these homologs are also comprehensively banned. On the basis of the results of the preliminary examination, SALDI-MS using the DIUTHAME chip was then applied to the analysis of DBDE in PS.…”