"Development of method for the determination of pesticides in food with high fat content"

The challenge of this thesis was to develop a method for determination of organochlorine, organophosphate and carbamate pesticides in fatty vegetable matrices such as olives, oilseed rape and avocado, and in fatty animal matrices such as fish tissues and liver of chicken. The pesticides extraction was carried out by Quick, Easy, Cheap, Effective, Rugged and Safe QuEChERS method, adapted for the analysis of pesticide residues in food matrices with high fat content, paying special attention the clean-up stage based on d-SPE technique. Multi-residue QuEChERS method was modified, testing two different extraction solvents (acetonitrile and ethyl acetate) and several d-SPE sorbents, of different retention mechanisms (PSA, GCB, C₁₈, SAX and NH₂), and its combinations depending on the nature and fat content grade of the samples, ready d-SPE clean-up tubes were also tested. The dual-d-SPE clean-up concept was first time introduced, it has advantages in the experimental cost, organic solvent and sorbent consumption, operation simplicity and time saving; it can achieve clean extracts free of fats and waxes, satisfying recoveries and high sensitivity. Low-temperature precipitation clean-up, freezing out, was coupled at the last stage of the procedure before GC-MS performance. The analysis of pesticide residues was performed by Gas Chromatography Ion Trap Mass Spectrometry (GC/IT-MS) working in Full Scan and SIM mode (Varian 4000 GC-MS) and by Gas Chromatography Quadrupole Mass Spectrometry (GC/Q-MS) working in SIM mode (Agilent 7890A GC/MS). Validation protocol met the criteria applied in the European Union in control of food and feed contaminants (SANCO document no. 12495/2011), recoveries were in the range from 70 to 120 % and repeatabilities were lower than 20%. Adequate sensitivity, linearity, reproducibility, accuracy, selectivity and precision were achieved. New easy, reliable, time and cost effective, robust, safety and environmentally friendly analytical method was developed for the determination of pesticide residues in vegetal and animal origin matrices with high fat content. The developed method was successfully applied analyzing pesticide residues in real samples; detectable pesticide residues were observed, but in all the cases the contamination level was lower than the maximum residue levels (MRLs) set by European Union (EU), Regulation (EC) N 396/2005. 

Abstract of the Doctoral Thesis: Development of method for the determination of pesticides in food with high fat content, developed by Juan Manuel Molina-Ruiz at the University of Agriculture in Krakow (Poland).