Critical validation of a GC-MS/MS methodology for confirmatory quantification of dioxins and PCBs in fish/ fish oil: Integrating a tiered surveillance strategy.

Dioxins and polychlorinated biphenyls (PCBs) are toxic, bioaccumulative persistent organic pollutants (POPs) requiring sensitive analysis in critical matrices, such as fish and fish products, to meet stringent regulatory standards. This study introduces a cost-effective complement to high-resolution mass spectrometry through a refined gas chromatography-tandem mass spectrometry workflow. The methodology integrates streamlined sample preparation, validation under European Union, 2017, and comprehensive measurement uncertainty estimation. Key performance metrics include low limits of quantification: 0.36 and 0.04 pg TEQ/g wet weight in fish, and 0.73 and 0.08 pg TEQ/g (12 % moisture basis) in fish oil for dioxins and dl-PCBs, respectively, along with 25.1 pg/g for ndl-PCBs in both matrices. Moreover, excellent linearity (R > 0.999), high accuracy (bias: ±20 %), strong precision (RSD < 15 %), and consistent internal standard recovery (70-105 %) ensured reliability and reproducibility. A practical multi-level pyramid framework is proposed for dl-POPs surveillance, enabling scalable and efficient monitoring-particularly valuable in resource-limited regions.