A Deans switch, employing Agilent's Capillary Flow Technology, was configured on an Agilent 7890A gas chromatograph (GC) equipped with dual electron capture detectors (ECDs). A method was developed for the analysis of fish oil for polychlorinated biphenyl (PCB) contamination. 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 onto 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 with a flame ionization detector (GC/FID) without backflushing. From these analyses, it was estimated that about two-thirds of the fish oil components would remain on the column after the 17.4-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. Evidence shows that backflushing removed the fish oil residue, which otherwise would quickly degrade the chromatography.
This document details a method developed by Agilent Technologies for the analysis of fish oil supplements for polychlorinated biphenyl (PCB) contamination. The method utilizes an Agilent 7890A gas chromatograph equipped with dual electron capture detectors (ECDs) and a Deans switch employing Capillary Flow Technology. Fish oil is directly injected after simple dilution, avoiding complex cleanup steps. The Deans switch performs heart cuts to separate seven indicator PCBs from the complex fish oil matrix.
| Gas chromatograph | Agilent 7890A |
|---|---|
| Automatic sampler | Agilent 7683B Series injector and tray |
| Primary column | J&W 30-m x 0.18-mm x 0.18-um DB-XLB |
| Secondary column | J&W 30-m x 0.25-mm x 0.50-um DB-200 |
| Inlet temperature | 330 °C |
| Dual ECD temperature | 340 °C |
| Post-Run Backflush duration | 24 min |
Fish oil from a supplement capsule is diluted 1:10 in isooctane and injected directly without cleanup steps.
Backflushing removes fish oil residue that would otherwise build up on the column, causing carryover and retention time shifts.