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The objective of this study was to develop a simple, sensitive and selective procedure for the preconcentration and determination of quercetin residues in Apium graveolens, Brassica oleracea, Spinacia oleracea, watercress, onion, and apple matrices. This novel method was developed on the basis of the dispersive-micro-solid phase extraction (D-μ-SPE) procedure based on a core–shell magnetic molecularly imprinted polymer (MMIP) in combination with high-performance liquid chromatography-ultraviolet (HPLC-UV). Variables affecting the quercetin extraction efficiency included pH, MIP dose, extraction contact time, elution organic solvent, and volume of organic solvent and were evaluated by the experimental central composite design (CCD). The obtained optimal parameters were as follows: pH (3.5), sorbent (12 mg), elution organic solvent and solvent volume (methanol, 0.2 mL), and elution time (22.0 min, without adding salt). The calibration curve was linear in the concentration range of 0.6–5500 μg L−1 with the lower limits of detection found in the range of 0.113–0.117 μg L−1, thereby revealing the high-sensitivity and -selectivity properties. The combination of D-μ-SPE and HPLC-UV could provide a method for the recovery of the analyte in various matrices at 22 min contact time with good reusability and excellent recoveries at four concentration levels (50, 100, 500, and 1000 μg L−1), ranging between 95.44 and 106.89% (relative standard deviation

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).

The present study attempted to develop a fast and sensitive ultrasound-assisted-dispersive-micro-solid phase extraction (UA-D-μ-SPE) method for the separation and preconcentration of albendazole (ABZ) from plasma and urine samples, using a molecularly imprinted polymer (MIP) coupled with high-performance liquid chromatography-UV (HPLC-UV). An MIP was selected as a sorbent, and the main factors viz. pH, MIP mass, sonication time, and eluent volume were optimized using CCD-RSM (central composite design-response surface methodology). Under the optimum conditions, the method showed the detection limit of 1.46, quantification of 4.86, and linear range of 10.0–6000.0 ng mL−1. The relative standard deviation and the relative recoveries of ABZ from spiked plasma and urine samples at five concentration levels (20, 50, 100, 500, and 1000 ng mL−1) were in the ranges of 1.43–5.21% and 92.48–101.40%, respectively. The kinetic sorption curve indicated that six min was sufficient to achieve sorption equilibrium for MIPNPs (MIP nanoparticles). The maximum sorption capacity was 34.9 mg g−1. All these results strongly support the high efficiency, selectivity, and sensitivity of the developed method for determining ABZ in plasma and urine samples.