Key Points
- Pesticides can persist within aquatic environments, and monitoring these substances requires highly sensitive and reliable analytical methods.
- Ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME) was combined with high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) to determine pesticide residues in different types of water samples.
- The IL-DLLME method was deemed a sensitive, precise, and eco-friendly alternative for routinely monitoring pesticide residues in water.
Researchers from Debre Berhan University (Ethiopia) and the University of South Africa (South Africa) combined ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME) with high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) to detect pesticide residues in water samples. Their findings were published in the Journal of Chromatography Open (1).
A significant environmental and public health concern is the occurrence of pesticide residues in aquatic environments. This can be attributed to their widespread use in agriculture and toxicity to non-target species. Pesticides can persist within aquatic ecosystems, presenting substantial risks to human health through exposure via drinking water and bioaccumulation. Monitoring pesticide residues in water requires highly sensitive and reliable analytical methods to detect trace levels, typically at concentrations as low as micrograms per liter (µg/L) or even lower. There is previous research that focused on pesticides in these environments. For example, scientists from the University of Santiago de Compostela developed a performance assessment of liquid chromatography quadrupole time-of-flight mass spectrometry (LC–QTOF-MS) operated in data-independent acquisition (DIA) mode that aimed to deliver both target quantification and suspect screening from a single chromatographic run (2).
Conventional extraction methodologies, such as liquid-liquid extraction (LLE) and solid-phase extraction (SPE), have been extensively implemented in pesticide analysis. However, they are subject to certain constraints, including considerable solvent consumption, extended processing times, and limited selectivity. To address these obstacles, ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME) was developed as a different approach for quantifying multiclass pesticides in aqueous matrices. According to the researchers, IL-DLLME can leverage the unique properties of ILs as extraction solvents, offering an environmentally sustainable alternative to traditional organic solvents. As for DLLME, it minimizes solvent utilization while achieving high enrichment factors, making it suitable for trace-level analysis.
In this research, IL-DLLME was integrated with high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) to quantify multiclass pesticides in aquatic samples. This methodology employs 1-Hexyl-3-methylimidazolium hexafluorophosphate ([C₁₀H₁₉N₂][PF₆]), 1-Octyl-3-methylimidazolium hexafluorophosphate ([C₁₂H₂₃N₂][PF₆]), and 1‑butyl‑3-methylimidazolium hexafluorophosphate ([C₈H₁₅N₂][PF₆]) as the extraction solvent, while methanol was used as the disperser solvent. Critical parameters that influence the extraction efficacy, encompassing the type and volume of extraction and disperser solvents, sample pH, and vortex conditions, were optimized. Under optimal conditions, the methodology exhibited commendable linearity (0.9974 ≤ R2 ≤ 0.9996), minimal limits of detection (0.1–1.3 µg/L) and quantification (0.3–3.9 µg/L), as well as satisfactory precision (relative standard deviation (RSD) ≤ 9.6 %). These were found across various water matrices, including tap water, groundwater, and river water.
Recovery rates (85–105%) met regulatory standards, confirming the method’s precision and robustness. 1-Hexyl-3-methylimidazolium hexafluorophosphate was also found to offer practical advantages, such as direct compatibility with high-performance liquid chromatography (HPLC) systems and reduced environmental impact, the latter of which can be attributed to its non-volatile nature.
Overall, the IL-DLLME method was deemed a sensitive, precise, and eco-friendly alternative for routinely monitoring pesticide residues in water. This aligns with modern principles of green analytical chemistry, offering practical advantages for environmental quality assessment.
References
(1) Negussie, B. T.; Dube, S.; Nindi, M. M.; Tesfaw, A. Optimization of the Ionic Liquid-Based Dispersive Liquid–Liquid Microextraction Combined with High-Performance Liquid Chromatography Coupled with Diode Array Detection for the Determination of Multiclass Pesticide Residues in Water Samples. J. Chromatogr. Open 2025, 8, 100231. DOI: 10.1016/j.jcoa.2025.100231
(2) Jones, K. A Novel LC–QTOF-MS DIA Method for Pesticide Quantification and Screening in Agricultural Waters. LCGC International 2025. https://www.chromatographyonline.com/view/a-novel-lc-qtof-ms-dia-method-for-pesticide-quantification-and-screening-in-agricultural-waters (accessed 2025-6-26)
