AbstractThe potential of a gas chromatographic method employing high‐resolution time‐of‐flight (TOF) mass spectrometry was evaluated for detection of polybrominated diphenyl ethers (PBDEs) in the environmental matrices represented by fish and river sediment. Two ionisation techniques, viz. electron ionisation (EI) and negative ion chemical ionisation (NICI), the latter with methane as a reagent gas, were used in this study. While the instrumental lowest calibration levels (LCLs) obtained in EI were in the range from 1 to 5 pg, their values ranged between 10 to 250 fg in NICI mode. This enhancement in detectability of target analytes enabled identification/quantification of even minor PBDE congeners, and consequently, improved characterisation of particular sample contamination patterns. In addition, this method allowed estimation of the PCB levels in examined samples. CB 153 was used as a contamination marker in this study.