GC-FID Method Detects Pesticides in Grape Juice

Researchers developed a sensitive, efficient way to test grape juice for five pesticides: two weedkillers (haloxyfop-R-methyl and oxadiazon) and three fungicides (diniconazole, tebuconazole, and difenoconazole). The method uses two quick cleanup steps to pull the pesticides out of the juice and concentrate them. In the first step, tiny particles of an absorbent material are mixed into the sample to capture the pesticides. In the second, a small amount of solvent is dispersed through the sample to draw them out further. The pesticides are then separated and measured using gas chromatography with flame ionization detection (GC-FID). A paper based on this work was published in the journal RSC Advances.¹

Why Is It Important to Test Grape Juice for Pesticides, and What Makes It So Challenging?

Because pesticides are used so heavily in modern farming, they now turn up widely in food and in the environment. Grapes and drinks made from them are especially likely to contain pesticides, partly because vineyards are sprayed so often and partly because the nature of grapes makes it easy for pesticides to stick to them and soak in. Even tiny amounts of pesticide left in grape juice raise serious concerns about food safety and public health, which is why sensitive and reliable ways of testing for them are needed.^2,3

Haloxyfop-R-methyl, oxadiazon, diniconazole, tebuconazole, and difenoconazole are weedkillers and fungicides that are commonly used in vineyards. Although they belong to different chemical families, they all tend to repel water and don’t dissolve well in it, which makes them hard to measure directly in watery liquids such as juice.^4,5 On top of that, grape juice is full of other substances, such as sugars, acids, color pigments, and plant compounds called phenolics, which can get in the way of the analysis and throw off the instrument’s readings. This is why it is important to clean up the sample and remove these substances before testing it.^6-8

How Did the Researchers Develop the Method, and How Well Did It Perform in Detecting Pesticides in Grape Juice?

To capture the pesticides, the researchers made a new plastic-like material using a simple chemical reaction between two common building blocks and then checked its makeup using standard lab tests. They fine-tuned the key settings for both cleanup steps to get the best results.¹

Under the best conditions, the method could detect the pesticides at very low levels, about 2 to 2.6 micrograms per liter, and measure them reliably from around 7 to 8.5 micrograms per liter. It gave accurate results over a very wide range of concentrations, up to 6,000 micrograms per liter. The cleanup steps concentrated the pesticides between about 365 and 495 times and recovered most of them, between 73% and 99%. Results were also very consistent, whether tests were repeated on the same day or on different days.¹

When the team tested real grape juice, other substances in the juice barely interfered with the results, and the amounts of pesticide measured were close to the amounts present, at 88% to 119%. The absorbent material could also be reused for four rounds of testing while still giving acceptable results.¹

“The proposed method,” write the authors of the paper,¹ “provided a simple, cost-effective, and reliable approach for the determination of pesticide residues in complex beverage matrices.” However, the authors point out that the method relies on a chlorine-containing solvent to pull out the pesticides, which makes it less environmentally friendly than it could be.¹

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References

1. Ershad, F.; Farajzadeh, M. A.; Mohammad Mehri, S. et al. Extraction of Some Pesticides from Grape Juice Samples Using an Amide-based Polymer as a Sorbent Followed by Gas Chromatographic Determination. RSC Adv. 2026. DOI: 10.1039/d6ra01736c
2. Fernandes, V. C.; Domingues, V. F.; Mateus, N. et al. Determination of Pesticides in Fruit and Fruit Juices by Chromatographic Methods. An Overview. J Chromatogr Sci. 2011, 49 (9), 715-730. DOI: 10.1093/chrsci/49.9.715
3. Radowan, A. A. A. Analytical Techniques for Determining Pesticide Residues in Food: A Comprehensive Review. Int. J. Mater. Tech. Innov. 2024, 4 (1), 42-74. DOI: 10.21608/ijmti.2024.298332.1105
4. Garcia-Cazorla, J.; Xirau-Vayreda, M. Persistence of Dicarboximidic Fungicide Residues in Grapes, Must, and Wine. Am. J. Enol. Vitic. 1994, 45 (3), 338-340. DOI:10.5344/ajev.1994.45.3.338
5. Ying, G. G.; Williams, B. Herbicide Residues in Grapes and Wine. J Environ Sci Health B 1999, 34 (3), 397-411. DOI: 10.1080/03601239909373205
6. Farajzadeh, M. A.; Khoshmaram, L.; Mogaddam, M. R. Combination of Solid-phase Extraction-hollow Fiber for Ultra-preconcentration of Some Triazole Pesticides Followed by Gas Chromatography-Flame Ionization Detection. J Sep Sci. 2012, 35 (1), 121-127. DOI: 10.1002/jssc.201100374
7. Koltappeh, S. A.; Ayazi, Z. Sustainable MOF-199/Chitosan Nanobiocomposite-Based Thin Film Microextraction for Multiresidue Determination of Pesticides in Fruits and Vegetables. Food Humanit. 2026, 101546. DOI: 10.1016/j.foohum.2026.101546
8. Hosseinian, S. B.; Ghani, M.; Raoof, J. B. Cellulose-supported MIL-101) Fe (/g-C3N4 as a Sustainable and Efficient Sorbent for Thin Film Microextraction of Organophosphorus Pesticides Followed by Determination Through HPLC-UV. Results Chem. 2026, 103624. DOI: 10.1016/j.rechem.2026.103624