GC and LC-IDMS/MS for Pesticide Residues in Cucumbers

Researchers who set out to present a metrologically reliable method for the simultaneous determination of 24 multi-class pesticide residues in cucumbers came up with a technique which couples a modified QuEChERS procedure with independent gas and liquid chromatography-isotope dilution tandem mass spectrometry (GC-IDMS/MS and LC-IDMS/MS). A paper based on their efforts was published in Food Chemistry.¹

Why Are Pesticides a Concern for Human Health?

Pesticides are a bit of a mixed blessing. On one hand, they are essential for keeping crops healthy, boosting harvests, and helping food last longer. On the other hand, using too much of them (or using them incorrectly) can cause them to build up in the human body over time. This buildup can be harmful, potentially damaging the nervous system, affecting fertility and reproduction, and weakening the immune system. In more serious cases, they have been linked to birth defects, cancer, and changes to our DNA.²

Why is the QuEChERS Method Widely Used for Pesticide Testing in Food?

Over the past two decades, the QuEChERS method has become the go-to way of extracting pesticides from food samples. Its popularity comes down to the fact that it is fast, straightforward, and doesn't require a lot of equipment or resources — living up to its name, which stands for "quick, easy, cheap, effective, rugged, and safe."³One of its biggest strengths is that it works well for a wide variety of pesticides, regardless of their chemical properties. It also uses less solvent and requires smaller sample sizes, making it a more environmentally friendly option. Over time, researchers have adjusted the original method to make it even more precise and reliable, particularly when working with specific types of food.^4,5

Was the Two-Method Testing Approach Accurate and Reliable Enough to be Trusted?

The researchers fine-tuned their two-method testing approach to account for common issues that can throw off results, like the sample not being fully extracted or the testing environment interfering with measurements. The final method performed very well across the board; it was highly accurate, consistent, and sensitive enough to detect substances even at the low levels set by food safety regulators. The two methods also agreed closely with each other, which confirmed that the results could be trusted.¹

The approach was used to officially certify three reference testing materials, with a high degree of confidence in the results. It also served as the gold-standard method for seven separate lab comparison programs. When the team tested 60 products from the market, they found that four out of ten exceeded the legal safety limits, a finding that raises serious concerns about food safety.¹

“The screening of commercial cucumber samples,” write the authors of the paper,¹ “indicated widespread MRL exceedances and the presence of banned pesticides, highlighting ongoing food safety risks. Together, this work presents a path toward more reliable pesticide residue monitoring and effective regulation to provide definitive data for reliable enforcement and public health protection.”
“The successful validation in cucumber,” they continue,¹ “a representative vegetable matrix, establishes a strong foundation for future work focusing on expanding the scope of analytes and adapting this robust framework to other challenging food matrices.”

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References

1. Zhou, S.; Wang, X.; Kan, Y. et al. Determination of Multi-Class Pesticide Residues in Cucumbers Using Modified QuEChERS Procedure Coupled with GC-IDMS/MS and LC-IDMS/MS. Food Chem. 2026, 519, 149761. DOI: 10.1016/j.foodchem.2026.149761
2. Alavanja, M. C.; Hoppin, J. A.; Kamel, F. Health Effects of Chronic Pesticide Exposure: Cancer and Neurotoxicity. Annu Rev Public Health 2004, 25, 155-197. DOI: 10.1146/annurev.publhealth.25.101802.123020
3. Anastassiades, M.; Lehotay, S. J.; Stajnbaher, D. et al. Fast and Easy Multiresidue Method Employing Acetonitrile Extraction/Partitioning and "Dispersive Solid-Phase Extraction" for the Determination of Pesticide Residues in Produce. J AOAC Int. 2003, 86 (2), 412-431. PMID: 12723926.
4. Wang, S.;Li, M.; Li, X. et al. A Functionalized Carbon Nanotube Nanohybrids-Based QuEChERS Method for Detection of Pesticide Residues in Vegetables and Fruits. J Chromatogr A 2020, 1631, 461526. DOI: 10.1016/j.chroma.2020.461526
5. 5.Wang, X.; Peng, H.; Wei, G. et al. QuEChERS Combined with Emulsification-Demulsification Clean-Up for Simultaneous Determination of Pesticide and Veterinary Drug Residues in Eggs by UPLC-MS/MS. Microchem. J.2025, 114116. DOI: 10.1016/j.microc.2025.114116