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In the present study, a novel ferrofluid was prepared by combining a menthol/thymol deep eutectic solvent with magnetic nanoparticles (Fe3O4@OA).

A simple, inexpensive, reliable and environmentally friendly method based on vortex-assisted dispersive liquid-liquid microextraction combined with solidification of a floating organic drop (VA-DLLME-SFO) followed by high performance liquid chromatography with a diode array detector (HPLC-DAD) was developed to determine benzoic acid (BA) and sorbic acid (SA) in ketchup and powder bags of instant noodles. Hydrophobic natural deep eutectic solvents (NADESs), as the microextraction solvent, were prepared with ternary components. Acetic acid can reduce the viscosity of hydrophobic NADESs and vortex can promote the dispersion of NADESs in aqueous solvents. In the DLLME process, several key parameters were optimized, including the type and volume of hydrophobic NADES, pH value, vortex time and salt content. Meanwhile, these parameters were assessed using response surface methodology based on the Box-Behnken design (BBD). Under optimal conditions, the developed method showed good linearity in the selected range (r2, 0.9997). The limits of detection were 0.2 μg mL-1 and 0.07 μg mL-1 for BA and SA, respectively. Recoveries were in the range of 82.21% to 102.70% and the relative standard deviations (intra-day and inter-day precisions) were less than 5.66%. The proposed method was successful in analyzing BA and SA in ketchup and powder bags of instant noodles.

A simple, rapid and sensitive method for the determination of four phenoxy carboxylic acid herbicides (4-chlorophenoxy acetic acid, 2-methyl-4-chlorophenoxy acetic acid, 2,4-dichlorophenoxy acetic acid and 2-(2,4-dichlorophenoxy)propionic acid) in food crops was established by magnetic multi-walled carbon nanotube assisted magnetic solid-phase extraction combined with dispersive liquid–liquid microextraction followed by ultra-high performance liquid chromatography-tandem mass spectrometry. In our current study, magnetic multi-walled carbon nanotubes were successfully synthesized and characterized by using Fourier transform infrared spectrometry, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry. The food crops were firstly pretreated with magnetic solid-phase extraction and the extracts were further purified by dispersive liquid–liquid microextraction. Various extraction factors were systematically optimized. Under the optimum conditions, satisfactory sensitivity levels were obtained with the method detection limits of 0.19–0.80 ng g−1 and method quantitation limits of 0.61–2.66 ng g−1. The recoveries of the four herbicides in different food crops ranged from 83.9 to 102.7% and the precision of the developed method was no more than 10.9%. Furthermore, the method was successfully applied to determine the four phenoxy carboxylic acid herbicides in real food crops (rice, millet, soy, oatmeal, and barley) with satisfactory results.

A sensitive and reliable analytical method for the simultaneous enantiomeric analysis of chiral non-steroidal anti-inflammatory drugs (ibuprofen, ketoprofen, and flurbiprofen) in water, river sediment, and sludge was established. Enantioseparation of the analytes was performed on a Chiralpak IG column using a mobile phase of 0.1% aqueous formic acid and acetonitrile. Magnetic solid-phase extraction, based on dummy-template molecularly imprinted polymer-coated magnetic multi-walled carbon nanotubes combined with dispersive liquid–liquid microextraction, was employed to pretreat complex environmental samples. Parameters affecting the extraction efficiency of the pretreatment processes were systematically optimized. Under the optimized conditions, recoveries of all enantiomers from environmental matrices were in the range 75.8–92.1% with relative standard deviations no higher than 12.4%. The quantification limits for enantiomers ranged from 6.17 to 11.94 ng L−1 in water samples and from 1.16 to 2.54 ng g−1 in river sediment and sludge samples. This method was successfully used to analyze the enantiomeric composition of three chiral non-steroidal anti-inflammatory drugs in real environmental samples, which will improve understanding of their degradation processes and aid evaluation of their ecological toxicity.

A rapid, simple and environmentally friendly method involving ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) coupled with ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) was developed for the simultaneous determination of nitroimidazoles (metronidazole and tinidazole) and amphenicol antibiotics (chloramphenicol and thiamphenicol) in water samples. In this work, the effective DLLME parameters such as pH, the type and volume of extraction solvent, the type and volume of dispersive solvent, salt concentration and extraction time were investigated. The significant factors were optimized and selected as follows: pH 4.0 water sample, 300 μL dichloromethane, 600 μL acetonitrile, no salt addition and 4 min of extraction time. Under the optimum conditions, the calibration curves were linear in the range of 2.00–100 ng L−1 (MNZ and TNZ) and 5.00–200 ng L−1(CAP and TAP) with regression coefficients (r) higher than 0.9917. Limits of detection (LODs) and limits of quantification (LOQs) were achieved in the range of 0.39–1.38 ng L−1 and 1.70–4.18 ng L−1, respectively. The relative recoveries of the analytes were from 82.8% to 99.5% with the relative standard deviations between 0.3% and 4.3%. The developed method was successfully applied to analyze the nitroimidazoles and amphenicol antibiotics in water samples with satisfactory results.

A novel and rapid microwave-assisted extraction (MAE) was optimized and compared with that of ultrasound-assisted extraction and heat reflux extraction for the quality control of ten index constituents in Cortex Juglandis Mandshuricae (CJM) based on a developed ultra-high performance liquid chromatography-tandem mass spectrometry method. The operation of MAE optimized through orthogonal array design experiments was performed at 70 °C for 8 min with ethanol–water (70:30, v/v) as the extracting solvent. The chromatographic separation was completed in a Waters ACQUITY UPLC® BEH Phenyl column (50 mm × 2.1 mm, 1.7 μm) with a gradient elution of acetonitrile and 0.1% (v/v) aqueous formic acid at a flow rate of 0.2 mL min−1. The method developed was validated with acceptable linearity (r > 0.999), intra- and inter-day precision, reproducibility, and extraction recoveries, and was applied successfully to analyzing 15 batches of CJM obtained from different regions of Northern China. The results were differentiated and classified by hierarchical cluster analysis (HCA), which indicated that the influence of CJM cultivation regions on the contents of index constituents was very obvious. The developed procedure is a promising analytical tool for the overall quality control of CJM.

A sensitive, wide-scope, and trace determination of nine residual pharmaceuticals in wastewater using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF MS) has been developed and validated. After solid-phase extraction with Cleanert PEP cartridges, sample extracts were analyzed by LC-QTOF MS for the simultaneous determination of levofloxacin, tetracycline, ketoprofen, meloxicam, lovastatin and fenofibrate in positive ion mode and chloramphenicol, diclofenac, and ibuprofen in negative ion mode. The separation and determination were performed on a C18 reversed-phase column (4.6 mm × 200 mm, 5 μm) under isocratic conditions. The pH value of the extracts, the type of SPE columns, and the MS conditions were optimized to increase the sample throughput and sensitivity. Quantitation was performed using external quantitation with standard solution mixtures. Under optimal conditions, the mean recovery for all the analytes from the water samples was more than 75.5%.