Combusted diatomaceous earth (DE, Thermo Fisher Scientific) was used as method blank. A total of 8 method blanks (one blank per sample batch), were included during extraction, clean up and quantification of the samples. Gas chromatography (GC) in tandem with Mass Spectrometry GC-MS/MS (Agilent 7000) in multiple reaction monitoring (MRM) mode was used to quantify all 209 congeners in 171 individual or coeluting congener peaks. The GC was equipped with a Supelco SBP-Octyl capillary column (30 m × 0.25 mm ID, 0.25 mm film thicknesses) with helium as carrier gas.

PCB congeners from blanks for estimating an individual PCB congener limit of quantification: Individual PCB congener mass in diatomaceous earth (DE) blank sample Quantification and determination of individual PCB congeners using GC-MS/MS