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Rapid determination of PCDDs, PCDFs and DL-PCBs in foods, feedingstuffs and vegetable oils using new modified acid silica

Ovanes Chakoyan

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (DL-PCBs) are persistent organic pollutants (POPs), which in the recent years received huge attention due to their extreme stability, high potential toxicity and bioaccumulation in food chains. Main source of human exposure to these compounds is discovered in foods of animal origin, especially foods rich of animal fat. The target of the present study was to set up an analytical method for the determination of PCDDs/PCDFs and DL-PCB in vegetable oils, sunflower meals, sunflower seeds, rapeseeds and milk powder. The first step consisted of a semi-automatic Soxhlet extraction for 3 hours, by using a mixture of Hexane: Acetone - 80: 20, followed by acid digestion with 55% acid silica, and filtration. After concentration, the extract is purified on multilayer column (silica gel, silica-KOH, silica-H2SO4 anhydrous Na2SO4) followed by an alumina column separation in two fractions (first fraction containing PCDDs/PCDFs, and the second containing only DL-PCBs). The purified extract was then analyzed by GC/MS/MS. The newly developed approach in our lab was capable to reduce the overall time of sample preparation down to seven hours/ per sample from initial of what time. Since the method shows good mean recoveries for all labelled congeners spiked in the samples (for PCDDs/PCDFs – 80-110%, for DL-PCBs – 70-85%), we assumed the absence of over estimation or underestimation in the analyzed samples.