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 《-》

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 ... -  《-》

In situ formation of thymol-based hydrophobic deep eutectic solvents: Application to antibiotics analysis in surface water based on liquid-liquid microextraction followed by liquid chromatography.

A simple and ecofriendly sample preparation method was developed for quantifying fluoroquinolone (FQ) antibiotics in surface water. Seventeen combinations of monoterpenes (menthol, thymol, and camphor), fatty acids (heptanoic, octanoic, nonanoic, and decanoic acids), and a benzoate ester (salol) were utilized for the in situ formation of hydrophobic deep eutectic solvents (hDESs) for liquid-liquid microextraction (LLME). The hDES comprising thymol and heptanoic acid (HA) exhibited the highest extraction efficiency for ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin. Optimization via the one-variable-at-a-time strategy revealed that a 2:1 ratio of thymol to HA yielded the highest efficiency for antibiotic extraction at pH 4-7. Further, response surface methodology-based optimization suggested that the optimal extraction conditions involved the use of appropriate amounts of thymol and HA to generate 100 μL of hDES in 10 mL of aqueous sample with incubation at 52 °C for 5 min, followed by automated shaking for 1 min. The collected hDES phase was diluted and subjected to liquid chromatography-ultraviolet detection analysis. The established method based on in situ formation of hDES coupled with shaker-assisted LLME (in situ hDES-SA-LLME) was validated. The method was specific and showed good linearity in the 15-3000 ng mL-1 concentration range (r2 ≥ 0.9997), with a limit of detection of 3.0 ng mL-1, limit of quantification of 9.0 ng mL-1, accuracy of 84.1-113.65%, and intra-day and inter-day precision of ≤7.78% RSD and ≤7.91% RSD, respectively. The method was successfully applied to three different types of real surface water samples. Without toxic volatile organic solvents, the developed method allows for safe and rapid, yet reliable, analysis of FQ antibiotics.

Li K ，Jin Y ，Jung D ，Park K ，Kim H ，Lee J ... -  《-》

Natural thymol-based ternary deep eutectic solvents: Application in air-bubble assisted-dispersive liquid-liquid microextraction for the analysis of tetracyclines in water.

Four new thymol-based ternary deep eutectic solvents were prepared and evaluated as the extractive phase in air-bubbles assisted dispersive liquid-liquid microextraction for extraction of tetracycline, doxycycline, and oxytetracycline from the water before high-performance liquid chromatography. The maximum extraction efficiencies were obtained using 400 μL of [choline chloride]:[thymol]:[nonanoic acid] in the molar ratio of 1:2:2 at pH = 5. The solvent was characterized by FTIR and NMR spectroscopy. The hydrophobicity of the deep eutectic solvent and its effect on the pH of water samples after mixing was also studied. Besides, the extraction efficiency of the ternary deep eutectic solvent was compared with that of two binary thymol-based deep eutectic solvents, including [choline chloride]:[thymol] and [thymol]:[nonanoic acid] at the same conditions. Under optimal conditions, limits of detection and quantification were 1.2-8.0 and 3.8-26.6 μg/L, respectively. The linear ranges were 18.2-500 μg/L for oxytetracycline, 26.6-500 μg/L for tetracycline, and 3.8-500 μg/L for doxycycline with the determination coefficients > 0.9912. Intra- and inter-day relative standard deviations were 1.2-3.8 and 7.7-11.2%, respectively. The developed method was applied to the analysis of tetracyclines in unspiked and spiked environmental water samples, and the obtained recoveries were 74.5-95.4% with relative standard deviations of 1.2-4.0%.

Sereshti H ，Abdolhosseini G ，Soltani S ，Jamshidi F ，Nouri N ... -  《-》

An effervescence-assisted switchable fatty acid-based microextraction with solidification of floating organic droplet for determination of fluoroquinolones and tetracyclines in seawater, sediment, and seafood.

Gao M ，Wang J ，Song X ，He X ，Dahlgren RA ，Zhang Z ，Ru S ，Wang X ... -  《-》