Ultrasound-assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplets coupled with gas chromatography for the determination of pesticide residues in water samples

An ultrasound-assisted dispersive liquid–liquid microextraction method based on solidification of floating organic droplets (UA-DLLME-SFO) followed by gas chromatography-flame ionization detection (GC-FID) was developed for the extraction and determination of pesticides including buprofezin, triazophos, λ-cyhalothrin, pyridaben, and es-fenvalerate in water samples. The influence of different parameters affecting the performance (the nature of extractant and disperser solvents as well as their volumes, salt addition, extraction and ultrasonication time) was evaluated in detail. Under the optimized conditions (extraction solvent: 8 μL 1-dodecanol; dispersive solvent: 300 μL acetonitrile; 1% (w/v) NaCl; ultrasonication time: 3 min), the obtained enrichment factors were between 143 and 813. The linear range was 0.20–200 μg L−1 with correlation coefficients higher than 0.9976. Based on a signal-to-noise ratio of 3, limits of detection were in the range of 0.11 to 0.48 μg L−1, depending on the compounds. Relative standard deviations (%) were less than 3.5% (n = 5) for both intra- and inter-day analyses. The proposed UA-DLLME-SFO-GC-FID method was successfully applied for the determination of pesticides in water samples with recoveries varying from 92.2 to 109.4%.