Selective Pressurized Liquid Extraction of PCB’s from Food and Feed Samples: Effects of High Lipid Amounts and Lipid Type on Fat Retention

Fat free extraction of polychlorinated biphenyls (PCBs) from fat containing food and feed matrices was achieved by selective pressurized liquid extraction using sulphuric acid impregnated silica inside 100 mL extraction cells on a Dionex ASE300. Data were compared to previous publications where extractions had been performed on a Dionex ASE200, with 33 mL cells and a Dionex ASE300, with 34 mL. In all extractions a high lipid amount of 1,500–3,000 mg was used in the extractions. Seven different fat/fat retainer ratios (FFRs) were tested (0.200, 0.150, 0.100, 0.075, 0.050, 0.040 and 0.025) at 100 and 150 °C using n-heptane as extraction solvent. The FFR ratio differed between triglycerides and fish oil in that fat free extracts were obtained at FFR of 0.050 for fish oil at 150 °C but 0.040 for fish triglycerides. When the extraction temperature was lowered to 100 °C a FFR ratio of 0.050 resulted in fat free extracts for both matrices. These data differ from previous studies, on ASE200 33 mL cells and ASE300 34 mL cells, were both matrices required a FFR of 0.025. The influence on the PCB recovery of these higher amounts of lipids in the extraction cells was tested by spiking triglycerides and fish oil with PCBs and extracting them with FFR-values of 0.025, 0.040 and 0.050. This showed that there was no difference in the PCB recovery and thus allowing a higher amount of lipids in each extraction cell when a FFR ratio of 0.050 could be used. The method was also tested on naturally contaminated cod liver homogenate, naturally contaminated cod liver oil spiked to feed for poultry, as well as certified reference materials (Cod liver oil BCR 349 and Spiked pork fat IRMM 445).