New Method for Analyzing GC-Amenable Pesticides in Animal Foods

A recent study by the European Union Reference Laboratory for Pesticides in Food of Animal Origin and Commodities with High Fat Content (EURL-AO) in Freiburg, Germany created a new method for analyzing gas chromatography (GC)-amenable pesticides in foods of animal origin. Their findings were published in the Journal of Chromatography A (1).

Tractor spraying young corn with pesticides | Image Credit: © marritch - stock.adobe.com

As food supply continues to become globalized, pesticide residue control is essential to comply with legislation and ensure food safety. In spite of pesticides being properly used, these substances can enter and accumulate in animal organisms through various pathways, such as deworming treatments, feeding contaminated feed and water, or through using hygiene products in stables; this accumulation can also transfer to animal foods, such as meat, milk, or eggs.

International organizations, such as the Codex Alimentarius Commission, the World Health Organization/Food and Agriculture Organization (WHO/FAO) of the United Nations, the European Union (EU), and national authorities, have set maximum residue levels (MRLs) for individual pesticides. Analyzing pesticides in food of animal origin is challenging due to complex matrices, as free fatty acids, triacylglycerides and phospholipids can contaminate the systems and affect the reproducibility of the signals (2). Multi Multi-residue methods usually consist of extraction, purification steps, and chromatographic measurements.

In this study, a novel automated sample preparation and purification method for various food matrices of animal origin was introduced. The tube drive system allows for quick fat extraction using a solvent mixture of cyclohexane, ethyl acetate, and acetonitrile. From the resulting fat extract, one aliquot is taken for clean-up, while another is taken for fat content determination, applicable to products with fat contents ranging from 1–30%. The automated clean-up process, which uses gel permeation chromatography and solid-phase extraction (primary secondary amine and C18 cartridge), was successfully validated for over 50 GC-amenable pesticides relevant to food of animal origin at a level of 10 µg/kg across each matrix. Further, 70% of analytes in milk (28 out of 40), 80% in cheese (34 out of 40), 82% in dairy products (38 out of 40), 82% in eggs (46 out of 56), and 85% in fish and offal (48 out of 56) were validated even at a lower level of 0.5 µg/kg. The pesticide spectrum was expanded further through a more comprehensive mix, which contained 196 GC-amenable analytes, spiked at a level of 10 µg/kg. Compared to other methods, analyte quantification increased by 40%, representing an increase from 09 to 150 analytes out of 196 in each matrix.

Through these experiments, optimized fat extraction was shown to improve laboratory workflow and significantly increase sample throughput in routine analysis. This method could be suitable for many foods of animal origin with fat content of 1–30%, while also being applicable to other matrices, such as gelatin, milk powder, or insects. Fat determination and automated clean-up for pesticide residues can also be performed from a single sample batch, thus eliminating the need for multiple arrays.

This new presented automated method (from raw extract to final measuring extract) proved reliable, easy-to-use, and allowed for reduced solvent consumption, thus enabling a continuous workflow around the clock. Further, by delivering clean extracts, it ensures good quantifiable signals, even with challenging matrices such as offal, while extending the range of analyte coverage by 40% compared to traditional methods.

References

(1) Buettner, A.; Polley, J.; Hardebusch, B.; Speer, K. Automation of a modular method (EN 1528) for analysis of GC-amenable pesticides in food of animal origin. J. Chromatogr. A 2025, 1741, 465620. DOI: 10.1016/j.chroma.2024.465620

(2) Hildmann, F.; Gottert, C.; Frenzel, T.; et al. Pesticide Residues in Chicken Eggs – A Sample Preparation Methodology for Analysis by Gas and Liquid Chromatography/Tandem Mass Spectrometry. J. Chromatogr. A 2015, 1403, 1–20. DOI: 10.1016/j.chroma.2015.05.024