Development of an eco-friendly approach based on dispersive liquid–liquid microextraction for the quantitative determination of quercetin in Nasturtium officinale, Apium graveolens, Spinacia oleracea, Brassica oleracea var. sabellica, and food samples

In this work, a fast, sensitive, inexpensive and environment-friendly dispersive liquid–liquid microextraction (DLLME) technique was developed based on solidification of floating organic drops (SFOD) for the preconcentration of quercetin followed by HPLC-UV. The parameters affecting the extraction efficiency (the type of extractant and disperser solvents and their volume, sample pH, concentration of salt, and sonication time) in the DLLME-SFOD-HPLC-UV method were studied and optimized with the aid of experimental designs. The optimum conditions found were as follows: extractant solvent type and amount, 0.25 mL of dodecanol, disperser solvent type and amount, 0.70 mL of acetonitrile, pH 5.0, extraction time of 0.5 min, and no need of adding salt. Under the optimal conditions, a good linearity in the range of 0.8–3500 μg L−1 was reached; furthermore, our proposed method had a reasonable reproducibility (RSD% 1.94–5.20), repeatability (RSD% 1.01–2.82), and recovery (96.65–106.76%). In addition, a low LOD (0.149–0.165 μg L−1), high enrichment factor, and very little extraction time were attained for different aqueous matrices (Nasturtium officinale, Apium graveolens, Brassica oleracea var. sabellica, Spinacia oleracea and food samples).