Quantification of PCBs was performed using a GC (Agilent
7890A) equipped with a mass-selective detector (Agilent 5975c)
in the negative chemical ionization (NCI) mode with methane used
as the reactant gas. The GC column used for quantification was a
DB-XLB fused silica capillary column (J&W Scientific Inc., Folsom,
CA) with 0.25 mm i.d. 60 m 0.25 lm film. PCB standards
were measured and the samples were analyzed separately in
selective ion monitoring (SIM) mode. The most abundant ions were
selected for quantification and two reference ions were used for the Arctic acts as a sink for PCBs as suggested by other studies