Screening for Dioxin-Like Compounds in Sediment and Fish Using a High-Resolution Time-of-Flight Mass Spectrometer

Poster Presentation

Presented by K. Chen
Prepared by

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Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and planar PCBs (pPCBs) are highly toxic and present at very low concentrations (ppt-ppq) in environmental samples. Therefore, highly sensitive and selective gas chromatography sector high-resolution MS (GC-HRMS) systems have been the gold standard for analysis of these compounds. In the last decade, GC triple quadrupole MS systems, due to their high sensitivity, became an alternative to the magnetic sector GC-HRMS. Recent developments in ion source, analyzer and detector design of high-resolution GC quadrupole time-of-flight MS (GC/Q-TOF) systems has resulted in improved sensitivity and resolving power (>25,000 at m/z 272). Such instruments may now be feasible alternatives to the magnetic sector instruments, offering high sensitivity, high selectivity and verification of identity through full-acquisition EI spectra. In this study, the performance of such a system was evaluated for the analysis of both biotic (fish) and abiotic (sediment) samples.

Samples were spiked with 13C-internal standards and extracted by Soxhlet (sediment) or column extraction (fish). Extracts were cleaned up using sulfuric acid treatment and carbon column fractionation using ISO/IEC 17025 accredited methods. The planar halogenated aromatic compound fraction from the carbon column was analyzed using 7250 GC/Q-TOF system.

There was good agreement with sector GC-HRMS data and the average in-house reference material (RM) values. For the toxicologically most relevant congeners (PCB126, 2,3,7,8-TCDD, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDD, 1,2,3,7,8- and 2,3,4,7,8-PeCDF) GC/Q-TOF results were within +/-25 % of the GC-HRMS and RM values. Similarly, the dioxin toxic equivalency values (TEQs) were within +/- 19 % of the reference data.

The sediment samples were also screened for dioxin-analogues such as polychlorinated naphthalenes (PCNs), polychlorinated dibenzothiophenes (PCDTs) and polychlorinated thianthrenes (PCTAs) and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs). Additionally, a non-target screening was employed to find other planar halogenated compounds.