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Identifying polar and non-target residues in food

The presence of potentially hazardous polar and non-target pesticides and veterinary drugs in food needs to be monitored to ensure their residues are not at levels that present a risk. However, highly polar analytes cannot usually be included in the official laboratory multi-residue methods that, in addition, only collect data for targeted compounds.
Identifying polar and non-target residues in food
The use of pesticides and veterinary drugs has changed through time, going from more persistent to more polar, readily degradable products. Due to their different physicochemical characteristics, these highly polar analytes, need specific analytical methods. Besides, the current existing methods only collect data for targeted compounds, so other potentially harmful, non-targeted analytes are not detected, although they can be present in the sample. These challenges were addressed by the CONFIRMS (Contaminant analysis in Food by Liquid Chromatography Mass Spectrometry: towards a generic extraction and screening for pesticides and veterinary drugs) project, which developed procedures for analysing highly polar and non-target contaminants in food samples by liquid chromatography (LC) coupled to different mass spectrometry (MS) detectors.

Different kinds of contaminants were selected for target analysis, among them, fourteen aminoglycosides (AGs), an important family of highly polar antibiotics, and very polar pesticides. Both groups of highly polar contaminants were analysed with Obelisc R, a zwitterionic hydrophilic interaction liquid chromatography (HILIC) stationary phase. AGs were extracted from liver, milk and honey samples with an acidic mixture and polymeric weak cation exchange solid phase extraction (SPE) and the procedure was validated. Very polar pesticides were extracted from fruits and vegetables with acidic methanol and cleaned with dispersive SPE to increase the sensitivity of the MS detector. Another family of contaminants, quaternary ammonium compounds (QACs), were also included in the project due to the extensive findings of their residues on foodstuffs. They were extracted from plants with the buffered QuEChERS version (AOAC 2007.01) without clean-up. The procedure was validated and five quantification methods were compared to compensate matrix effects being the most accurate the non-linear standard addition method. Project work also included training for the non-target analysis of water samples and their post-target processing.

Presentations at three international conferences showed chemists, veterinarians and legislators how the techniques developed by CONFIRMS can be used to control problematic highly polar analytes. CONFIRMS successfully developed procedures for three families of highly polar pesticides and veterinary drugs in food that were directly implemented in an official routine laboratory in target and non-target approaches.

Related information

Keywords

Pesticides, veterinary drugs, polar analytes, aminoglycosides, food, quaternary ammonium compounds
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