Hydrophobic Deep Eutectic Solvent in Vortex-Assisted Liquid–Liquid Microextraction for Pesticide Analysis by Gas Chromatography

A green and practical method was developed for the screening of pesticide residues in fruit juice samples using a deep eutectic solvent (DES)-based microextraction technique coupled with gas chromatography–flame ionization detection (GC-FID). The DES, synthesized from thymol and octanoic acid at a 1:2 molar ratio, was employed in a vortex-assisted dispersive liquid–liquid microextraction (VA-DLLME) system, with ethanol serving as a sustainable dispersive solvent. This method enabled efficient extraction and preconcentration of six organophosphates and two pyrethroid pesticides. Complete chromatographic separation was achieved within 11 min. To ensure accurate quantification in complex matrices, matrix-matched calibration (MMC) was employed for each fruit juice type. Calibration curves were constructed using blank matrix extracts spiked with standard pesticide solutions, allowing compensation for matrix effects, such as signal suppression or enhancement. The use of MMC, combined with matrix-specific blank corrections, significantly improved analytical reliability and accuracy. The method exhibited excellent analytical performance, with limits of detection ranging from 0.6 ng L–1 to 0.06 mg L–1, enrichment factors between 56 and 168, and acceptable precision (RSD < 4.3% for repeatability; < 6.7% for reproducibility). The simplicity, affordability, and reliability of GC-FID render the method highly suitable for routine testing in industrial and service laboratories. Although ideal for rapid screening, confirmatory MS analysis is recommended for complex or unknown matrices. Representative chromatograms support the method’s reliability and validate its practical utility for pesticide residue analysis in fruit juice samples.