A Simplified Multi-Residue Method Using μSPE Clean-Up Combined with Gas Chromatography-High Resolution Mass Spectrometry for the Determination of 250 Pesticide Residues in Cow’s Milk

The complexity of the milk matrix, driven by its lipid-rich composition, complicates pesticide residue analysis. This study developed a simplified and robust analytical procedure for the quantification of 250 pesticides in cow’s milk. Sample preparation involved acidified ethyl acetate extraction followed by centrifugation at 0 °C. A subsequent clean-up step was performed using micro solid-phase extraction (μSPE) in a 96-well format with the enhanced matrix removal-lipid (EMR-lipid) sorbent. Final extracts were analyzed by gas chromatography coupled to high-resolution mass spectrometry (GC-Q-Orbitrap-MS). Method validation demonstrated satisfactory linearity within the 5–100 µg/L range, recoveries between 70.6% and 119.8%, and precision, expressed as relative standard deviation (RSD), was acceptable for both intraday (1.8–19.2%) and interday (1.6–18.5%) conditions. The limit of quantification (LOQ) was set at 10 µg/kg for all compounds. The method was applied to 23 commercial cow’s milk samples, and no pesticide residues were detected above the current European Union (EU) maximum residue limits (MRLs).