A gas chromatography/micro-electron capture detector (GC/micro-ECD) method was developed for the analysis of fish oil for polychlorinated biphenyls (PCBs) using a Deans switch based on Capillary Flow Technology.The Deans switch was used to heart-cut 7 indicator PCBs (IUPAC congeners 28, 52, 101, 118, 138, 153, and 180) from the primary DB-XLB column on to a DB-200 column for further separation.Fish oil from a supplement capsule was simply diluted 1∶10 in isooctane and injected directly.In a separate experiment, the fish oil was analyzed by GC/FID without backflushing.From these analyses, it was estimated that about 2/3 of the fish oil components would remain on the column after the 18.6-minute GC/ECD run.To prevent carryover, contamination, and retention time shifts, the Deans switch was used to backflush the primary column at the end of each run.The constant retention times for individual congeners during 100 injections of 10% fish oil samples shows that backflushing for 3 minutes was sufficient to remove the fish oil residues.The method detection limits (MRL) for these indicator congeners were less than 1.0 ng/g in fish oil except PCB congener 28 (MDL is 5.0 ng/g).