Bisphenols are common additives in everyday products like plastics and food can linings. The most widely known analogue, bisphenol A (BPA), has been subjected to restrictions on its use by both government decree and consumer-driven initiatives due to its known toxicity and estrogenic activity. However, other, less familiar bisphenols may exhibit even greater toxicity and stronger estrogenic activity than BPA.
Zhao et al. (2016) recently applied accurate-mass Orbitrap tandem mass spectrometry (MS/MS) to nine bisphenols (plus corresponding isotope-labeled compounds) in order to compose characteristic fragmentation pathways and deduce elemental compositions for major product ions.1 They believe this data could assist researchers in identifying bisphenols and their metabolites in the future, particularly in complex matrices. For MS data acquisition and processing, the researchers used an UltiMate 3000 UHPLC system coupled with a Q Exactive Focus Hybrid Quadrupole-Orbitrap mass spectrometer, as well as Xcalibur software (all Thermo Scientific).
Table 1. Investigated bisphenols and accurate mass values
|
Bisphenol |
Accurate mass (m/z) |
|
Bisphenol A (BPA) |
228.11503 |
|
Bisphenol B (BPB) |
242.13068 |
|
Bisphenol C (BPC) |
256.14633 |
|
Bisphenol P (BPP) |
346.19328 |
|
Bisphenol F (BPF) |
200.08373 |
|
Bisphenol S (BPS) |
250.02998 |
|
Bisphenol Z (BPZ) |
268.14633 |
|
Bisphenol AF (BPAF) |
336.05850 |
|
Bisphenol AP (BPAP) |
290.13068 |
The research team produced accurate mass values and elemental compositions for precursor ions and main product ions for all bisphenols here and used these to construct proposed fragmentation pathways. For some product ions, this represented a first reported detection. The researchers report agreement between the isotope-labeled compounds and the unlabeled bisphenols.
Zhao et al. found similar fragmentation patterns for the bisphenols analyzed here. Notable commonalities included:
- Six bisphenols formed a common phenoxide product ion (C6H5O, m/z 93): BPA, BPB, BPF, BPZ, BPP and BPAP.
- Five bisphenols lost a phenol group (C6H5OH) and formed a common product ion [M-H-C6H60]: BPA (m/z 133.06488), BPB (m/z 147.08046), BPF (m/z 105.03353), BPZ (m/z 173.09624) and BPAP (m/z 195.08082); a sixth bisphenol, BPS, has a sulfur atom substitution in its structure, resulting in a C6H5O loss instead.
- Four bisphenols formed the product ion [M-H-CH4] and its oxidized structures: BPA (m/z 211.07618), BPB (m/z 225.09156), BPC (m/z 239.10758) and BPP (m/z 329.15443). The team observed that each of these compounds carried two methyl groups at the central carbon atom (except for BPB, which carried one methyl group and one ethyl group), indicating the oxidized ions likely formed as a result of free radicals there.
Overall, the researchers offered the first proposed characteristic fragmentation pathways for nine bisphenols using accurate mass MS/MS data, including some novel product ion identifications. They reported similar patterns and neutral losses among the analyzed compounds and consistent results between labeled and unlabeled analytes. The research team believes the data provided here could assist researchers in identifying bisphenols and bisphenol metabolites in both in vitro and in vivo experiments and may be of particular value when working with complex matrices.
Reference
1. Zhao, H., et al. (2016) “Investigation on fragmentation pathways of bisphenols by using electrospray ionization Orbitrap mass spectrometry,” Rapid Communications in Mass Spectrometry, 30(16) (pp. 1901–1913), doi: 10.1002/rcm.7666.
Post Author: Melissa J. Mayer. Melissa is a freelance writer who specializes in science journalism. She possesses passion for and experience in the fields of proteomics, cellular/molecular biology, microbiology, biochemistry, and immunology. Melissa is also bilingual (Spanish) and holds a teaching certificate with a biology endorsement.
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