Comparison of efficiency of different sorbents used during clean-up of extracts for determination of polychlorinated biphenyls and pesticide residues in low-fat food

A model mixture (containing α-linolenic acid as interfering substance) for polychlorinated biphenyls (PCBs) and organochlorine pesticides determination was subjected to clean-up with various solid-phase extraction (SPE) columns. Octadecylsilyl (C-18), graphitised non-porous carbon (Envi-Carb), aminopropyl (NH2), Florisil and Alumina SPE sorbents were evaluated. The relative sample clean-up provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The Florisil, Alumina and NH2 columns were found to provide the most effective clean-up, removing the greatest amount of interfering substance, and simultaneously ensuring analyte recoveries higher than 70% for most compounds. The Envi-Carb and C-18 columns did little to eliminate matrix interferences. The developed clean-up procedure has been applied to real low-fat food samples, such as herring (Clupea harengus). Recoveries >78% with standard deviations (SD) <15% were obtained for all compounds under the selected conditions. Method quantification limits (MQLs) were in the 5–10 μg/kg range.