Determination of pesticide residues in fish tissues by modified QuEChERS method and dual-d-SPE clean-up coupled to gas chromatography-mass spectrometry

The aim of this research was to modify the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for the determination of organochlorine and organophosphate pesticides in fatty animal matrices such as fish muscle tissues of carp and sturgeon collected from Carp Valley, Lesser Poland. Pesticides extraction effectiveness was evaluated at 0.030 mg kg(-1) spiking level and efficiency of the dispersive-solid-phase extraction (d-SPE) clean-up step was evaluated by comparison testing two different d-SPE clean-up stages, first the addition of the d-SPE sorbent combination (PSA + SAX + NH2), and secondly the addition of C18 after extracts enrichment with the d-SPE sorbent combination (PSA + SAX + NH2), introducing a novel concept of clean-up named dual-d-SPE clean-up. Analysis of pesticide residues was performed by Gas Chromatography Quadrupole Mass Spectrometry (GC/Q-MS) working in selected-ion monitoring (SIM) mode. Linear relation was observed from 0 to 200 ng mL(-1) and determination coefficient R(2) > 0.997 in all instances for all target analytes. Better recoveries and cleanliness of extracts in both samples, carp and sturgeon tissues, were obtained after C18 addition during the dual-d-SPE clean-up step. Recoveries were in the range 70-120%, with relative standard deviation lower than 10% at 0.030 mg kg(-1) spiking level for most pesticides. LODs ranged 0.001-0.003 mg kg(-1), while LOQs ranged 0.004-0.009 mg kg(-1). The proposed method was successfully applied analyzing pesticide residues in real carp and sturgeon muscle samples; detectable pesticide residues were observed, but in all of the cases contamination level was lower than the default maximum residue levels (MRLs) set by the European Union (EU), Regulation (EC) N 396/2005.