Application of deep eutectic solvent based dispersive liquid–liquid microextraction method followed by HPLC-DAD for quantification of selected neonicotinoid pesticides in vegetable oils
Musiiwa V. Sengane, Masixole Sihlahla, Philiswa N. Nomngongo, Nomvano Mketo
Abstract
• A greener deep eutectic solvent-based liquid-liquid extraction of neonicotinoids from vegetable oils was successfully developed. • Optimal conditions were 0.8 mL DES volume, 4.5 min extraction time, 0.5 mL eluent volume, 7 pH and 75 s elution time. • The DES-LLME method achieved high extraction recoveries ranging from 79-119. 58% and good precision of 0.1-1. 62%. • The three green assessment tools (NEMI, AGREE and BAGI) confirmed that the DES-LLME was green. • The investigated NEOs were not detectable in avocado, canola, olive and sunflower using DES-LLME followed by HPLC-DAD. The use of deep eutectic solvents (DES) as alternative green solvents in various analytical chemistry fields has garnered attention of researchers globally. Therefore, this study presents environmentally friendly DES for extraction of selected neonicotinoids (acetamiprid, imidacloprid, thiacloprid and thiamethoxam) prior to their determination using high-performance liquid chromatography- diode array detector (HPLC-DAD). The DES mixture that resulted in the highest extraction recoveries of neonicotinoids (NEOs) was choline chloride with ethylene glycol (CCl:EG) and nuclear magnetic resonance and Fourier transform infrared confirmed the successful synthesized CCl:EG. Thereafter, the CCl:EG was applied in dispersive liquid–liquid microextraction (DLLME) for the preconcentration and extraction of acetamiprid, imidacloprid, thiacloprid and thiamethoxam. The optimum factors affecting extraction efficiency of the DES-DLLME procedure were 0.8 mL (DES volume), 4.5 min (extraction time), 0.5 mL (eluent volume), 7 pH and 75 s (eluent time). The optimized DES-DLLME achieved limit of detection (LOD) and quantification (LOD) range of 0.4–4.95 ng.µL −1 and 1.43–9.70 ng.µL −1 respectively. Additionally, the extraction method achieved good accuracy (79.0–119.6 %), preconcentration factors (39.3–118), interday (0.61–1.62 %) and intraday (0.1–0.98 %) precisions. The greenness assessment of the proposed DES-DLLME method using AGREE, NEMI and AES tools revealed that the method was green. Finally, the developed DES-DLLME method was applied to real vegetable oils and the concentrations were below detection limits.