Supramolecular solvents based on hydrophobic natural deep eutectic solvents and primary amines for preconcentration and determination of enrofloxacin in milk.

In this work, coacervation in primary amines solutions with hydrophobic natural deep eutectic solvents based on terpenoids and carboxylic acids was demonstrated for the first time. A liquid-phase microextraction approach was developed based on supramolecular solvent formation with primary amine acting as amphiphile and hydrophobic deep eutectic solvent making up mixed vesicles and serving as coacervation agent. Such supramolecular solvents could be used to separate wide range of substances from different aqueous media, such as food products, biological liquids and wastewaters. It is important that both hydrophobic and ionic interactions with supramolecular aggregates take place ensuring synergetic effect and better extraction ability, which is significant in separating relatively polar analytes. Different primary amines and deep eutectic solvents were investigated for liquid-phase microextraction of proof-of-concept amphoteric analyte (enrofloxacin, widely used veterinary fluoroquinolone antibiotic) and its determination by high-performance liquid chromatography with fluorescence detection using Shimadzu LC-20 Prominence chromatograph and RF-20A fluorescence detector. It was found that the supramolecular solvent based on 1-nonylamine, formed after addition of a deep eutectic solvent based on menthol and hexanoic acid (molar ratio of 1:1), provided maximum extraction recovery (85 %) and maximum enrichment factor (34). To characterize the extraction system, the composition of the phases was investigated, and cryo-transmission electron microscopy images were obtained. Vesicular aggregates were observed in the supramolecular solvent. The extraction mechanism was proposed in terms of formation of mixed aggregates to capture the analyte. Limit of detection was found to be 7 μg kg-1, while linear range of 20-250 μg kg-1 was established. Relative standard deviation values were lower than 7 %. Relative bias did not exceed 12 %.

Kurashov Y ，Pochivalov A ，Petrova A ，Safonova E ，Garmonov S ，Bulatov A ... -  《-》

An effervescence-assisted dispersive liquid-liquid microextraction based on three-component deep eutectic solvent for the determination of fluoroquinolones in foods.

An effervescence-assisted dispersive liquid-liquid microextraction approach using three-component deep eutectic solvent based on short-chain and medium-chain carboxylic acids and terpenoid was developed for the first time. The microextraction procedure was applied to the determination of fluoroquinolone antibiotics in foods (milk and shrimp samples) by high-performance liquid chromatography with fluorometric detection. In this microextraction procedure three-component deep eutectic solvent acted as a proton donor agent and an extractant. The carbon dioxide bubbles caused by the fast reaction between precursor of deep eutectic solvent (short-chain carboxylic acid) and effervescent agent (sodium carbonate) promoted the dispersion of the extractant in an aqueous sample phase. Various carboxylic acids were studied as hydrogen bond donors for the formation of deep eutectic solvents and proton donor agents for the generation of CO2 bubbles. Two natural terpenoids (menthol and thymol) were studied as the hydrogen bond acceptors for the formation of three-component solvent. The extraction system based on heptanoic acid and thymol (1:2, mol/mol) containing formic acid (proton donor for generating CO2 bubbles) provided maximum extraction recovery (86-99%) and a higher extraction efficiency of analytes compared to their extraction into individual hydrophobic precursors of the system. The LODs, calculated from the blank tests based on 3σ, were varied from 0.03 to 0.06 μg L-1 and from 0.3 to 0.6 μg kg-1 for fluoroquinolone antibiotics in milk and shrimp samples, respectively. The proposed approach provided effective dispersion of extractant speeding up the extraction process and fast separation of phases without any external energy assistance.

Barbayanov K ，Timofeeva I ，Bulatov A 《-》

In matrix formation of deep eutectic solvent used in liquid phase extraction coupled with solidification of organic droplets dispersive liquid-liquid microextraction; application in determination of some pesticides in milk samples.

In this work, a liquid-phase extraction procedure and dispersive liquid-liquid microextraction method based on deep eutectic solvents were combined and used for the simultaneous extraction of different classes of pesticides; including carbaryl, hexythiazox, pretilachlor, iprodione, famoxadone, sethoxydim and fenazaquin from milk samples. In the first step, a deep eutectic solvent was synthesized in milk sample and simultaneously, was used for extraction of the analytes along with precipitation of milk proteins. To assist the formation of the deep eutectic solvent and increasing the mass transfer rate of the analytes, ultrasonic irradiations was used. In the second step, the collected organic phase from pervious step was mixed (as dispersive solvent) with a water-immiscible deep eutectic solvent (ChCl: decanoic acid) and injected into deionized water. The cloudy solution was placed into an ice bath and the extraction solvent was solidified on the top of the solution. After removing the solid phase by a spatula, it was melted at room temperature and 1 μL of the extraction solvent was injected into the separation system. Under the optimum extraction conditions, low limits of detection and quantification within the ranges of 0.90-3.9 and 3.1-13 ng mL-1 were achieved, respectively. Precision of the method expressed as relative standard deviation was in the ranges of 3.8-5.3 and 4.8-6.9 for intra- and inter-day (n = 5) precision, respectively, at a concentration of 50 ng mL-1 of each analyte. Extraction recoveries and enrichment factors were between 64 and 89% and 320 and 445, respectively. Lastly, several milk samples were successfully analyzed using the proposed method.

Jouyban A ，Farajzadeh MA ，Afshar Mogaddam MR 《-》

Microextraction of Tigecycline Using Deep Eutectic Solvents and Its Determination in Milk by LC-MS/MS Method.

Kiszkiel-Taudul I ，Stankiewicz P 《-》

Vortex-assisted dispersive liquid-phase microextraction for the analysis of main active compounds from Zi-Cao-Cheng-Qi decoction based on a hydrophobic deep eutectic solvent.

In this study, a vortex-assisted hydrophobic deep eutectic solvent dispersive liquid-phase microextraction was developed and used for the extraction and preconcentration of six main active compounds in Zi-Cao-Cheng-Qi decoction. The deep eutectic solvent, prepared by mixing tetrabutylammonium chloride and hexanoic acid at a molar ratio of 1:1, was added to the sample solution containing the analytes. In the absence of disperser, the extractant was rapidly dispersed into fine droplets by the aid of vortex and adequately contacted with the analytes. Some key parameters affecting the approach including extraction solvent type and volume, sample phase pH, extraction time, centrifugation time, and salt concentration were investigated and optimized. Under the optimum conditions, enrichment factors of the target analytes were in the range of 3-330. The calibration graphs were linear with a correlation coefficient (r) ≥ 0.9929. The detection limits were 0.3-0.9 ng/mL, and the satisfactory precisions (relative standard deviations, 0.5-8.9%) and accuracies (relative recoveries, 91.1-102.2%) were also obtained. The developed method was rapid (only 2 min), eco-friendly, effective, and easy to operate. And it has been successfully applied to simultaneous extraction, enrichment, and determination of the main active compounds in a traditional Chinese medicinal formula coupled with high-performance liquid chromatography.

Xue J ，Yang L ，Chen X ，Bai XH ，Hu S ... -  《-》