Compound-specific stable carbon and bromine isotope analysis tracking transformation mechanisms of organobrominated contaminants: a review of principles, methodologies and applications

Abstract

Organobrominated contaminants, such as brominated flame retardants (BFRs), pose significant environmental risks due to their persistence, toxicity, and complex transformation pathways. Compound-specific stable isotope analysis (CSIA) of carbon (δ¹³C) and bromine (δ⁸¹Br) has emerged as a powerful tool to elucidate degradation mechanisms, particularly debromination processes that are critical to understanding environmental fate. This review synthesizes principles, methodologies, and applications of CSIA-C/Br for tracking the transformation of organobrominated pollutants, emphasizing advances in overcoming analytical challenges. Traditional techniques such as gas chromatography-quadrupole mass spectrometry (GC-qMS) and inductively coupled plasma mass spectrometry (ICP-MS) often struggle with precision and matrix interference, especially for high-boiling-point polybrominated compounds. Innovations such as Orbitrap high-resolution mass spectrometry enable precise separation of different isotopologues, minimizing isobaric interferences and enhancing reliability, with high potential for precise bromine isotope analysis. The review also underscores the urgent need for internationally certified bromine isotope reference materials and expanded isotopic databases to improve cross-laboratory comparability. By integrating carbon and bromine isotope data, this CSIA-C/Br offers transformative insights into reaction pathways, supporting environmental forensics and pollutant management. Future work must prioritize refining analytical precision, addressing low-magnitude bromine isotope effects, and advancing field-compatible methods to bridge laboratory findings with real-world environmental systems.