Multi-residue determination of polyhalogenated carbazoles in aquatic sediments

Recent studies have discovered a number of polyhalogenated carbazoles (PHCZs) in aquatic sediments and soil. These substances are attracting emerging concern due to their environmental presence, persistence, and potential dioxin-like activities. In response to the increasing interests in these chemicals, the present study aimed to develop an efficient and sensitive analytical methodology for quantitative determination of environmentally relevant PHCZs in aquatic sediments. The developed method employed time- and solvent-saving extraction and cleanup procedures and utilized gas chromatogram-mass spectrometry (GC-MS) for separation and determination of PHCZ analytes. PHCZs substituted with bromine atom(s) (except for 3-bromocarbazole) or a combination of bromine and chlorine atoms were analyzed by GC-MS in the electron-capture negative ionization (ECNI) mode, whereas congeners substituted with chlorine atoms as well as 3-bromocarbazole were analyzed in electron impact (EI) ionization mode. The developed method demonstrated negligible matrix effects, satisfactory and stable recoveries, and low method limits of quantification (0.11-0.53 ng/g dry weight (dw)) of target analytes. Using this method, we successfully determined a number of PHCZs in surface sediments from the Saginaw River system (Michigan, USA) and the Saginaw Bay of Lake Huron, with the summed concentrations of PHCZ congeners ranging up to 46.3 ng/g dw. Given that further investigations are needed to better elucidate the sources, environmental behavior, fate, and toxicity of PHCZs, highly sensitive and efficient analytical methodologies would be essentially needed to fill in these knowledge gaps.