Application of matrix solid-phase dispersion to the determination of polychlorinated biphenyls in fat by gas chromatography with electron-capture and mass spectrometric detection.

A one-step extraction-purification method for the determination of polychlorinated biphenyls (CBs) in fat samples was developed. Matrix solid-phase dispersion using different combinations of normal phase sorbents and elution solvents was evaluated, in terms of extraction yield and lipids removal efficiency, for the isolation of CBs from butter, chicken and beef fat. Under optimal conditions, 0.5 g of sample was dried with anhydrous sodium sulphate, dispersed on 1.5 g of Florisil and transferred to the top of a polyethylene solid-phase extraction cartridge which already contain 5 g of Florisil. Non-coplanar CBs were quantitatively eluted with 15 ml of n-hexane. The lipid percentage in this extract remained below 0.06% of the sample mass. As coplanar congeners show a higher affinity for Florisil, 20 ml of hexane-dichloromethane (90:10) were necessary for the quantitative recovery of coplanar and non-coplanar CBs. The potential of the procedure to fractionate non-coplanar and coplanar congeners is discussed. After extract evaporation to 0.2 ml, quantification limits of 0.4 ng of each CB per g of fat were achieved, using gas chromatography with tandem MS or electron-capture detection (ECD).