New advance in the application of compound-specific isotope analysis (CSIA) in identifying sources, transformation mechanisms and metabolism of brominated organic compounds

Abstract

Brominated organic compounds (BOCs) originate from nature and anthropogenic activities, and are plentiful in the environment. Most BOCs are hazardous and pose significant risk to the environment and human health. Controlling these pollutants requires understanding their sources, behaviors, and final environmental fates. Compound-specific isotope analysis (CSIA), which has been a new important tool for scientific breakthrough in many research areas, such as environmental, ecological, and geochemical sciences, can help scientists elucidate the sources, transformation pathways and fates of BOCs. The appearance of gas chromatography combustion isotope ratio mass spectrometry (GC/C/IRMS) and gas chromatography multiple collector inductively coupled plasma mass spectrometry (GC/MC/ICPMS) in the past decades, has greatly developed the application of CSIA for the stable isotope analysis of BOCs. This review first describes the current analytical methods for measuring the carbon, hydrogen, oxygen and bromine stable isotopes of BOCs using mass spectrometry. Then, the review discusses the application for identifying sources, tracing transformation pathways and biological metabolisms. This includes a discussion of the kinetic isotope effects (KIEs), evaluated using (bio)chemical reaction, based on the reaction mechanism. Finally, the review highlights the future challenges and prospects regarding bromine isotope effects, multiple isotope enrichment, and position-specific isotope analysis. This review ends with a perspective on future activities that may benefit the development of the fast-growing field of CSIA.