Homogeneous liquid-liquid microextraction based on deep eutectic solvents

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 %.

Cyclodextrin-based ternary supramolecular deep eutectic solvents for efficient extraction and analysis of trace quinolones and sulfonamides in wastewater by adjusting pH

BACKGROUND

Antibiotics residues can accelerate the growth of drug-resistant bacteria and harm the ecological environment. Under the effect of enrichment and biomagnification, the emergence of drug-resistant pathogenic bacteria may eventually lead to humans being ineffective to drugs in the face of bacterial or fungal disease infections in the future. It is urgent to develop an efficient separation medium and analytical method for simultaneous extraction and determination of antibiotics in the water environment.

RESULTS

This work doped 2,6-Di-O-methyl-β-cyclodextrin, randomly methyl-β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin with thymol:fatty acid respectively to construct non-covalent interaction-dominated pH-responsive ternary supramolecular deep eutectic solvents (SUPRADESs), which can undergo a hydrophilic/hydrophobic transition with aqueous phase to achieve an efficient microextraction. Semi-empirical method illustrated that SUPRADESs have a wide range of hydrogen bond receptor sites. We developed a SUPRADES-based analytical method combined with liquid chromatography-triple quadrupole mass spectrometry for the extraction and determination of trace quinolones and sulfonamides in wastewater. The overall limits of detection of the method were 0.0021-0.0334 ng mL-1 and the limits of quantification were 0.0073-0.1114 ng mL-1. The linearity maintained good in the spiked level of 0.01-100 ng mL-1 (R2 > 0.99). The overall enrichment factors of the method were 157-201 with lower standard deviations (≤8.7).

SIGNIFICANCE

The method gave an extraction recovery of 70.1-115.3 % for 28 antibiotics in livestock farming wastewater samples from Zhejiang, China, at trace levels (minimum 0.5 ng mL-1). The results demonstrated that inducing the phase transition between SUPRADES and aqueous phase by adjusting pH for extraction is a novel and efficient pretreatment strategy. To our knowledge, this is the first application of cyclodextrin-based ternary SUPRADESs with pH-responsive reversible hydrophobicity-hydrophilicity transition behavior in wastewater analysis.

High-throughput semi-automated emulsive liquid-liquid microextraction for detecting SDHI fungicides in water, juice, and alcoholic beverage samples via UHPLC-MS/MS

Herein, a High-Throughput Semi-automated Emulsive Liquid-Liquid Microextraction (HTSA-ELLME) method was developed to detect Succinate Dehydrogenase Inhibitor (SDHI) fungicides in food samples via UHPLC-MS/MS. The Oil-in-Water (O/W) emulsion comprising a hydrophobic extractant and water was dilutable with the aqueous sample solution. Upon injecting the primary emulsion into the sample solution, a secondary O/W emulsion was formed, allowing SDHI fungicides to be extracted. Subsequently, a NaCl-saturated solution was injected in the secondary O/W emulsion as a demulsifier to rapidly separate the extractant, eliminating the need for centrifugation. A 12-channel electronic micropipette was used to achieve a high-throughput semi-automation of the novel sample pretreatment. The linear range was 0.003-0.3 μg L-1 with R2 > 0.998. The limit of detection was 0.001 μg L-1. The HTSA-ELLME method successfully detected SDHI fungicides in water, juice, and alcoholic beverage samples, with recoveries and relative standard deviations of 82.6-106.9% and 0.8-5.8%, respectively. Unlike previously reported liquid-liquid microextraction approaches, the HTSA-ELLME method is the first to be both high-throughput and semi-automated and may aid in designing pesticide pretreatment processes in food samples.

Simple and rapid ionic liquid-based one-, two-, three-phase transition microextraction for efficient extraction of trace organic pollutants and elimination of lipid co-extractives from fatty food matrices

Extraction of trace contaminants from fatty food matrices is challenging in food analysis. Herein, a new ionic liquid-based one-, two-, three-phase transition microextraction (IL-OTTPTME) was proposed to efficiently extract trace targets while simultaneously eliminating lipid co-extractives. The method performance was illustrated through the determination of chrysoidine in fatty soybean products using high-performance liquid chromatography-ultraviolet/visible detection. The strong interactions and infinite contact between IL and chrysoidine in the one-phase system ensured ultra-high extraction efficiency (∼100 %). Density functional theoretical calculations confirmed the presence of strong hydrogen bonding and π-π interactions. The formation of the three-phase system during extraction could completely eliminate lipid co-extractives. The IL-OTTPTME integrated extraction, enrichment and cleanup steps into one step, making it rapid and extremely easy to operate. The method had a wide linear range of 0.5-5000 μg/kg and low limit of detection (0.15 μg/kg). It also had satisfactory relative recoveries (95.1 %-104.0 %) and low RSDs (≤5.0 %, n = 5).

Determination of copper in rose tea samples using flame atomic absorption spectrometry after emulsification liquid-liquid microextraction

Rose tea infusion has gained popularity worldwide due to its health benefits. However, it is known that tea plants can be contaminated with heavy metals including copper. Hence, an accurate and applicable analytical method namely emulsification liquid-liquid microextraction based deep eutectic solvent - flame atomic absorption spectrometry (ELLME-DES-FAAS) was proposed to determine copper at trace levels in rose tea samples. Under the optimum experimental conditions, analytical figures of merit for the developed method were examined, and dynamic range, limit of detection (LOD) and limit of quantification (LOQ) were found to be 5.07-246.61 µg/kg (mass-based) with 0.9992 coefficient of determination, 2.50 µg/kg and 8.32 µg/kg, respectively. A matrix matching calibration strategy was employed to boost recovery results, and the acceptable recovery results were recorded between 95.9 % and 118.4 %. According to recovery results, the developed analytical method can be safely employed to determine the concentration of copper in rose tea samples accurately.

Utilization of a pH-switchable hydrophilicity solvent for the microextraction of clomipramine from human urine samples

Clomipramine (CLP) is a tricyclic antidepressant drug, and its determination in biological samples is of high importance in clinical and forensic evaluations to assure appropriate drug concentrations. In the present study, benzoic acid was employed as a pH-switchable hydrophilicity solvent (SHS) for the microextraction of CLP from authentic human urine samples prior to its determination by high performance liquid chromatography-ultraviolet detection (HPLC-UV). The microextraction protocol was based on the phase transition of the SHS through pH alteration that resulted in its rapid dispersion and simultaneous phase separation. The obtained solid was collected in a syringe filter, dissolved in methanol, and analyzed. The main parameters that affected the efficiency of the microextraction procedure were studied and optimized to ensure high extraction efficiency for CLP and the analytical method was validated. Under optimum conditions, good linearity was observed between 0.05 and 5.0 μg mL-1. The limit of detection and limit of quantification were found to be 0.015 and 0.05 μg mL-1, respectively. The RSD values for intra-day repeatability and inter-day precision were 2.4-8.9 % and 1.7-9.1 %, respectively. The relative recovery values were within 90.0 and 110.0 % in all cases, demonstrating good method accuracy. The proposed SHS microextraction showed cost-efficiency, handling simplicity, and rapidity resulting in enhanced sample throughput. Moreover, the proposed method exhibited a green character and good applicability based on its evaluation by Green Analytical Procedure Index and Blue Applicability Grade Index.

Predicting the formation of NADES using a transformer-based model

The application of natural deep eutectic solvents (NADES) in the pharmaceutical, agricultural, and food industries represents one of the fastest growing fields of green chemistry, as these mixtures can potentially replace traditional organic solvents. These advances are, however, limited by the development of new NADES which is today, almost exclusively empirically driven and often derivative from known mixtures. To overcome this limitation, we propose the use of a transformer-based machine learning approach. Here, the transformer-based neural network model was first pre-trained to recognize chemical patterns from SMILES representations (unlabeled general chemical data) and then fine-tuned to recognize the patterns in strings that lead to the formation of either stable NADES or simple mixtures of compounds not leading to the formation of stable NADES (binary classification). Because this strategy was adapted from language learning, it allows the use of relatively small datasets and relatively low computational resources. The resulting algorithm is capable of predicting the formation of multiple new stable eutectic mixtures (n = 337) from a general database of natural compounds. More importantly, the system is also able to predict the components and molar ratios needed to render NADES with new molecules (not present in the training database), an aspect that was validated using previously reported NADES as well as by developing multiple novel solvents containing ibuprofen. We believe this strategy has the potential to transform the screening process for NADES as well as the pharmaceutical industry, streamlining the use of bioactive compounds as functional components of liquid formulations, rather than simple solutes.

A eutectogels-catalyzed one-pot multi-component reaction: access to pyridine and chromene derivatives

The demand for a wide array of functional chemicals and materials has experienced a significant surge in tandem with the advancement of civilization. Regrettably, a number of perilous solvents are employed in chemical laboratories and industrial settings, posing significant risks to the well-being of researchers and contributing to environmental degradation through pollution. Eutectogels, which are based on the eutectic concept, may be synthesized by self-assembling or self-polymerization of various components when put under UV irradiation (254 nm). A novel copolymeric deep eutectic solvent (DES) was successfully synthesized, comprising choline chloride (HBA) as the hydrogen bond acceptor, acetamide (HBD) as the hydrogen bond donor, tetraethyl orthosilicate (TEOS), and formic acid. In this study, we present the preparation of four-component ETGs for synthesizing pyridine and chromene derivatives as a reusable catalyst through a multi-component pathway without solvents. The procedure of synthesizing these heterocyclic compounds is free of using toxic solvents and it could be categorized as a green method.

Deep eutectic solvents in sample preparation and determination methods of pesticides: Recent advances and future prospects

This review summarizes recent advances of deep eutectic solvents (DESs) in sample preparation and determination methods of pesticides in food, environmental, and biological matrices since 2019. Emphasis is placed on new DES categories and emerging microextraction techniques. The former incorporate hydrophobic deep eutectic solvents, magnetic deep eutectic solvents, and responsive switchable deep eutectic solvents, while the latter mainly include dispersive liquid-liquid microextraction, liquid-liquid microextraction based on in-situ formation/decomposition of DESs, single drop microextraction, hollow fiber-liquid phase microextraction, and solid-phase microextraction. The principles, applications, advantages, and limitations of these microextraction techniques are presented. Besides, the use of DESs in chromatographic separation, electrochemical biosensors, fluorescent sensors, and surface-enhanced Raman spectroscopy are discussed. This review is expected to provide a valuable reference for extracting and detecting pesticides or other hazardous contaminants in the future.

Separation and identification of snuff constituents by using GC-MS and ICP-OES as well as health risk assessment of some existing heavy metals

The identification of volatile organic components in snuff was accomplished using GC-MS analysis in this study. The findings of the GC-MS analysis revealed the presence of nicotine, its derivatives, and several other toxic chemicals that are hazardous to human health. Furthermore, the content of 34 elements in four brands of snuff consumed in Neyshabur City was determined by ICP-OES analysis (with five repetitions). The health hazards of measured heavy elements were examined from two perspectives: carcinogenic (7 heavy elements were checked) and non-carcinogenic (4 heavy elements were checked). The investigation of non-carcinogenic hazards from inhalation was based on the computation of the hazard quotient (HQ) factor, and the results indicated that inhaling five heavy metals, Cu, Pb, Ni, Zn, and Cd, does not represent a substantial health risk ((HQ < 1). In contrast, the computed HQ factors for Cr and As were relatively high (1 < HQ < 10), indicating a substantial health risk from breathing these two elements. The carcinogenic factor (CR value) results revealed that the degree of carcinogenic risk for Cd was very low (CR value less than 1 × 10-6) and did not pose a concern to the consumer population. However, the risk of As, Cr, and Ni exposure is considerable in the carcinogenic risk range (CR values between 1 × 10-6 and 1 × 10-4).

Microextraction of essential oils: A review

Liquid phase microextraction (LPME) and solid phase microextraction (SPME) are popular extraction techniques for sample preparation due to their green and highly efficient single-step extraction efficiency. With the increasing attention to essential oils, their evaluation and analysis are significant in analytical sciences. In this review, starting from a brief description of the recent advances in the last decade, the attention has been focused on the up-to-date research works and applications based on liquid and solid phase microextraction for essential oil analyses. Particular attention has been given to the approaches using ionic liquids, eutectic solvents, gas flow assisted, and novel composite materials. In the end, the technological convergence of novel microextraction of essential oils in the future has been prospected.

Deep eutectic solvent-based manganese dioxide nanosheets composites for determination of DNA by a colorimetric method

BACKGROUND

Nucleic acid is the carrier of genetic information and the keymolecule in life science. It is important to establish a simple and feasible method for nucleic acid quantification in complex biological samples.

METHODS

Four kinds of hydrogen bond acceptors (choline chloride (ChCl), L-carnitine, tetrabutylammonium chloride (TBAC) and cetyltrimethylammonium bromide (CTAB)) were used to synthesize deep eutectic solvents (DESs) with hexafluoroisopropanol (HFIP). DESs based manganese dioxide (MnO2) nanosheets composites was synthesized and characterized. DNA concentration was determined by a UVVis spectrometer. The mechanism of DNA-DES/MnO2 colorimetric system was further discussed.

RESULTS

The composite composed of DES/MnO2 exhibited excellent oxidase-like activity and could oxidize 3,3',5,5' -tetramethylbenzidine (TMB) to produce a clear blue change with an absorbance maximum at 652 nm. When DNA is introduced, the DNA can interact with the DES by hydrogen bonding and electrostatic interactions, thereby inhibiting the color reaction of DES/MnO2 with TMB. After condition optimization, ChCl/HFIP DES in 1:3 molar ratio was used for the colorimetric method of DNA determination. The linear range of DNA was 10-130 µg/mL and exhibited good selectivity.

CONCLUSION

A colorimetric method based on DES/MnO2 was developed to quantify the DNA concentration. The proposed method can be successfully used to quantify DNA in bovine serum samples.

Hexafluoroisopropanol-based deep eutectic solvents for high-performance DNA extraction†

In this study, hexafluoroisopropanol (HFIP)-based deep eutectic solvents (DESs) were developed and used for DNA extraction from human whole blood samples for the first time. HFIP-based DESs were prepared using HFIP and choline chloride (ChCl)/tetrabutylammonium chloride/cetyltrimethylammonium bromide as the hydrogen bond donor and acceptor, respectively. The two-phase system formation was promoted with different inorganic salts as the phase-forming component. According to the strong phase separation capability and high DNA extraction efficiency, DESs consisting of HFIP/ChCl-(NH₄)₂SO₄, HFIP/ChCl-Na₂SO₄ and HFIP/ChCl-MgSO₄ were then selected for application in DNA extraction. The factors that could have impacted the DNA extraction process, including molar ratio of DES, DES addition, salt species and addition, and sample pH, were systematically investigated via single-factor experimental analysis. Furthermore, we selectively examined bovine serum albumin and RNA to assess the specificity of the HFIP-based DESs for DNA extraction. Conclusively, 93.9%, 96.7% and 99.8% DNA could be extracted using the HFIP/ChCl-(NH₄)₂SO₄, HFIP/ChCl-Na₂SO₄, and HFIP/ChCl-MgSO₄ systems, respectively. Moreover, the developed systems were successfully used to extract DNA from human whole blood with satisfactory results. The DNA secondary structure was stable after DES extraction with the electrostatic interaction between DES and DNA as the main force driving DNA adsorption by DES.

In a novel approach, hexafluoroisopropanol-based deep eutectic solvents were synthesized and utilized as an efficient alternative for extracting DNA from human whole blood.

A Simple High-Throughput Field Sample Preparation Method Based on Matrix-Induced Sugaring-Out for the Simultaneous Determination of 5-Hydroxymethylfurfural and Phenolic Compounds in Honey

In the present work, a high-throughput field sample preparation method was reported for the simultaneous determination of 5-hydroxymethylfurfural and phenolic compounds in honey. Combining a simple and green homogenous liquid−liquid extraction, matrix-induced sugaring-out, with the use of a 96-deepwell plate and multichannel pipette, the proposed method showed its merits in instrument-free and high-throughput preparation. Due to the high-throughput property, the parameters of the method were rapidly and systematically studied using a constructed 4 × 2 × 4 × 3 array (sample amount × ratio of ACN:H2O × standing time × replicates) in a 96-deepwell plate. Analytical performance was fully validated, and the limits of detection and limits of quantification were in the range of 0.17−1.35 μg/g and 0.51−4.14 μg/g, respectively. Recoveries were between 83.98 and 117.11%, and all the precisions were <5%. Furthermore, the developed method was successfully applied in the outdoor preparation of commercial honey samples and the in-field preparation of raw honey samples in apiary. The current work presented a simple, rapid, and high-throughput method for the field sample preparation of honey and provides a valuable strategy for the design of field and on-site sample preparation.