Structural elucidation of bisphenol E and bisphenol S photoinduced by-products by high-resolution electrospray ionisation mass spectrometry and tandem mass spectrometry.

Rationale: Bisphenol E (BPE) and bisphenol S (BPS) have recently replaced bisphenol A as monomers for producing polycarbonates. However, BPE and BPS can pose hazards as they are known to be endocrine disruptors. Despite the huge increase in their use, there is a lack of data regarding the toxicity and effects of BPE and BPS.
Methods: We investigated the photoinduced transformation of BPE and BPS when subjected to sun-simulated radiation and using TiO ₂ as a photocatalyst. Analyses of BPE, BPS and their by-products were performed by high-performance liquid chromatography/high-resolution mass spectrometry (HPLC/HRMS) using an orbitrap mass analyzer in negative electrospray ionisation (ESI) mode. The chromatographic separations were achieved by employing a C18 reversed-phase column, and the transformation products (TPs) were elucidated structurally using HRMS and multistage MS experiments performed in collision-induced dissociation (CID) mode.
Results: The transformation of bisphenol S involved the formation of twelve by-products, while ten TPs were detected following BPE degradation. For bisphenol S, the cleavage of the molecule is a very important transformation route, together with the hydroxylation of the substrate to provide mono- and poly-hydroxylated TPs. For bisphenol E, the two main routes were hydroxylation and ring opening. Acute toxicity for BPS, BPE and their TPs was assessed using the Vibrio fischeri assay, highlighting that their initial transformation involved the formation of TPs that were more toxic than the parent compound.
Conclusions: The HPLC/HRMS method developed was useful for characterising and identifying newly formed TPs from bisphenol E and bisphenol S. This study aimed to examine the structure of twenty by-products identified during TiO ₂ -mediated photolysis and to evaluate acute toxicity over time.
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