The current work reports the development and validation of a qualitative screening method for 156 pesticides in Atlantic salmon feeds based on the use of ultrahigh-performance liquid chromatography (UHPLC) coupled to traveling-wave ion mobility spectrometry (TWIMS)/quadrupole time-of-flight mass spectrometry (QTOFMS). This novel hyphenation allows a straightforward estimation of the collision cross section (CCS), a physicochemical property that recently has been proposed as an additional identification point for pesticides.
In order to increase the overall efficiency of the screening workflow, data processing parameters and tolerances involved in the automated analyte detection were first optimized. The use of the CCS as an additional identification point greatly improved the method selectivity, decreasing the rate of false-positive detections in blank feed samples. Qualitative validation was then performed in accordance with the EU document SANTE/11945/2015 on analytical quality control and validation procedures for pesticide residues analysis in food and feed. Feed samples were spiked with 156 pesticides at three levels (0.01, 0.05 and 0.20 mg/kg) and analyzed by the proposed method. Under the optimized conditions, screening detection limits (SDLs) ≤0.05 mg/kg were achieved for 82% of the investigated pesticides.
The applicability of this new approach for the screening of pesticides was finally proven by analyzing several commercial Atlantic salmon feed samples as well as various plant-based feed ingredients. Pirimiphos-methyl and ethoxyquin were among the most frequently detected analytes in the investigated samples.