In situ formation of natural deep eutectic solvent on membrane after fat hydrolysis for lindane isomers determination in peanut paste.

In this work a sample pretreatment approach assumed liquid-liquid microextraction based on the in situ formation of a hydrophobic natural deep eutectic solvent on a hydrophobic membrane impregnated with natural terpenoid was developed. The procedure included alkaline hydrolysis of a food sample containing fat to form fatty acids, which acted as precursors for the in situ formation of the deep eutectic solvent with natural terpenoid. Two processes were observed on the membrane surface: in situ formation of the hydrophobic deep eutectic solvent and liquid-liquid microextraction of the target analytes. After microextraction, the membrane containing the analytes was easily removed from the sample solution. The developed approach was applied to the separation and preconcentration of hydrophobic organochlorine pesticides (ɑ-hexachlorocyclohexane and γ-hexachlorocyclohexane) from a hydrophobic sample matrix (peanut paste), followed by their determination by gas chromatography with electron capture detection. Under optimal conditions, the limits of detection and quantification for both analytes were 0.3 and 1.0 µg kg-1, respectively. The procedure allowed the separation of fat-soluble analytes from a complex sample matrix with a high content of fat. The extraction recoveries were in the range of 93-95 %.

Selective extraction of plant bioactive compounds with deep eutectic solvents: Iris sibirica L. as example.

INTRODUCTION: Deep eutectic solvents (DESs) are promising extractants with tuneable properties. However, there is a lack of reports about the influence of the nature of the original DES on obtaining the metabolomic profile of a plant. OBJECTIVE: The aim of this study is to investigate the possibility of obtaining Iris sibirica L. chromatographical profiles with DESs based on various hydrogen bond donors and acceptors as extraction solvents. METHODOLOGY: DESs were prepared by mixing choline chloride or tetrabutylammonium bromide with various hydrogen bond donors and investigated for the extraction of bioactive substances from biotechnological raw materials of I. sibirica L. The obtained extracts were analysed by HPLC with diode array detector (DAD) and Q-MS. RESULTS: Chromatographic profiles for I. sibirica L. extracts by eight choline chloride DESs and six tetrabutylammonium DESs have been obtained. It has been found that selective recovery of bioactive substances can be achieved by varying the composition of DESs. Eleven phenolic compounds were identified in I. sibirica L. using HPLC-MS. Phase separation was observed with acetonitrile for four DESs. New flavonoid derivatives have been found in DES extracts compared with methanol extracts. CONCLUSION: The results showed the possibility of DES usage for extraction without water addition. Selectivity of DESs varies depending on the chemical composition of hydrogen bond donors and acceptors. Choline chloride is a more suitable hydrogen bond acceptor for the flavonoid extraction. Choline chloride-lactic acid (1:1) DES has demonstrated a metabolic profile that was the closest to the methanol one and enhanced the extraction up to 2.6-fold.

Fast and ecofriendly triple sulfonamides mixture utilization using UV irradiation and spherical SnO2 nanoparticles with controllable parameters and antibacterial activity.

One of the solutions for the growing problem of water purification is photocatalytic degradation of the pollutants. Semiconductor nanoparticles are widely under study as a promising photocatalyst for this purpose. However, there is still lack of understanding of the relation between properties of nanoparticles, in their turn related with synthesis conditions, and photocatalytic efficiency, as well as of the other factors influencing the process. For the first time, a possibility to regulate photocatalytic activity of SnO2 nanoparticles under UV light via regulation of structural parameters is shown. A method for obtaining spherical nanoparticles with different parameters was developed. Obtained nanoparticles were fully characterized. Special attention was paid to the study of oxygen vacancies. With the help of quantum computational methods, it was shown, that the concentration of vacancies is around 1 per 32 tin atoms. Obtained data on oxygen vacancies were further used for the evaluation of pollutant-nanoparticle surface interaction to get closer to the calculations of real systems. On the example of methylene blue, it was shown that the greater is the amount of oxygen vacancies and the lower the amount of defects, the higher photocatalytic activity. The obtained dependence is confirmed by the fact that the photoresponse increases with a decrease of amount of defects in the sample. Degradation kinetics of sulfonamides mixture was studied, and its dependence on active complex formation was shown based on the quantum chemical calculation data. Degradation of antibiotics in water from Neva River reached more than 95% in 35 min, which indicates that developed photocatalyst efficiency is not affected by pollutants contained in open water in the centre of the metropolis. It was shown, that the use of nanoparticles allows to speed up the process of bacteria destruction under UV light, which indicates the antibacterial activity of obtained nanoparticles.

Three-component deep eutectic solvent-based microextraction approach for biodiesel quality control: Determination of water and metals.

Biodiesel is an important alternative fuel produced by blending biofuels with petroleum diesel. Biofuel production is usually carried out by catalytic interesterification of animal fats or vegetable oils, followed by the removal of by-products and catalysts through washing with water. Residual amounts of water and catalysts can accelerate fuel biodegradation and contribute to the corrosion of metal surfaces. Considering the need to control the quality of biodiesel fuel, a simple and environmentally friendly analytical approach was first developed for the determination of water and metals (sodium, potassium, magnesium, calcium as catalysts, and iron, copper, tin, zinc, lead as feedstock elements) using a deep eutectic solvent. The technique involved microextraction of analytes from biodiesel into a new three-component deep eutectic solvent (choline chloride, lactic acid, and cobalt chloride) using a laboratory vortex, followed by impregnating the filter paper with the obtained extract to determine the analytes. The colorimetric determination of water is based on a change in the color of the deep eutectic solvent, which goes from blue to pink due to the formation of cobalt aqua complexes. The detection of water on the filter paper was carried out using a conventional scanner. The content of metals on the filter paper was determined by X-ray fluorescence spectrometry. Under optimal conditions, the detection limit was 100 mg kg-1 for water and 0.03-3 mg kg-1 for metals. The technique enabled multicomponent analysis to be carried out without the use of dangerous Karl Fischer reagents (for water determination) and microwave mineralization of samples (for elemental analysis). The enrichment factor ranged from 290 to 330, and the RSD was less than 15%.

Deep eutectic solvents with low viscosity for automation of liquid-phase microextraction based on lab-in-syringe system: Separation of Sudan dyes.

In the work limitations of deep eutectic solvents in the flow-based analysis are discussed. Deep eutectic solvents based on terpenes and fatty acids with low viscosity were studied as extraction solvents for liquid-liquid microextraction into a lab-in-syringe system for the first time. As a result an automated deep eutectic solvent-based microextraction approach was proposed. The procedure involved aspiration of deep eutectic solvent (based on terpene and fatty acid) and aqueous sample solution followed by phases mixing by a magnetic stirrer inside a syringe of flow system. After phase separation the extract phase was transferred from the syringe into a vial followed by analysis by a high-performance liquid chromatography with diode-array detection. The determination of Sudan I, Sudan II and Sudan III in chili-based sauces was considered as an analytical task. The mass-transfer intensification performed by the magnetic stirring inside the syringe allowed to perform fast (2 min) and efficient (extraction recoveries 87-95%) extraction. The limits of detection, calculated from a blank test based on 3σ, were from 0.003 to 0.005 mg kg-1, RSD was <9%. The microextraction procedure did not involve the use of hazardous organic solvents, only 100 µL of natural deep eutectic solvent was required for dyes preconcentration.

Stir membrane liquid-phase microextraction based on milk fats hydrolysis and deep eutectic solvent formation: Determination of bisphenols.

In this paper, a stir membrane liquid-phase microextraction approach based on milk fats hydrolysis and in situ deep eutectic solvent formation was developed for the first time. The approach was applied to clean-up and preconcentrate bisphenols from milk samples. The procedure assumed alkaline hydrolysis of samples fats to obtain water-soluble salts of fatty acids that acted as precursors for the deep eutectic solvent formation. A stir membrane disk impregnated with menthol was placed into the sample solution. The formation of microdroplets of the hydrophobic fatty acids was observed under sample acidification. Collection of the extract phase on the disk was based on deep eutectic solvent formation. Under optimal conditions, the RSD was < 6 %, limits of detection for bisphenols were 0.3-0.5 µg kg-1. The extraction recoveries were in the range of 95-97 %, which indicated the excellent capability of the developed approach to extract hydrophobic analytes from complex matrices.

Deep Eutectic Solvents or Eutectic Mixtures? Characterization of Tetrabutylammonium Bromide and Nonanoic Acid Mixtures.

Deep eutectic solvents have quickly attracted the attention of researchers because they better meet the requirements of green chemistry and thus have the potential to replace conventional hazardous organic solvents in some areas. To better understand the nature of these mixtures, as well as expand the possibilities of their use in different industries, a detailed examination of their physical properties, such as density, viscosity, the nature of the interactions between their constituents, the phase diagrams, depression of their melting point, and interpretation of these results is necessary. In this work, the mixtures of tetrabutylammonium bromide (TBAB) and nonanoic acid (NA) in different molar ratios are theoretically and experimentally investigated by applying a phase diagram constructed on the basis of differential scanning calorimetry measurements and COSMO-RS model. Spectral properties are investigated based on Fourier transform infrared spectroscopy and density functional theory. The observed eutectic point indicates the formation of a DES in the TBAB-NA system in a 1:2 molar ratio. This is due to the presence of hydrogen bonds between the carboxyl group from the NA molecule and the bromine atom from the TBAB molecule. Other eutectic mixtures are most likely the solutions of TBAB in NA, in which hydrogen bonds predominate between acid molecules.

Direct Laser Writing of Copper Micropatterns from Deep Eutectic Solvents Using Pulsed near-IR Radiation.

In this study, we developed a method for the fabrication of electrically conductive copper patterns of arbitrary topology and films on dielectric substrates, by improved laser-induced synthesis from deep eutectic solvents. A significant increase in the processing efficiency was achieved by acceptor substrate pretreatment, with the laser-induced microplasma technique, using auxiliary glass substrates and optional laser post-processing of the recorded structures; thus, the proposed approach offers a complete manufacturing cycle, utilizing a single, commercially available, pulsed Yb fiber laser system. The potential implications of the presented research are amplified by the observation of laser-induced periodic surface structures (LIPSSs) that may be useful for the further tuning of tracks' functional properties.

Deep eutectic solvents based on carboxylic acids for metals separation from plant samples: Elemental analysis by ICP-OES.

Deep eutectic solvents based on choline chloride, carboxylic acids, urea, and polyols were investigated for separation of 14 metals from plant samples. It was found that carboxylic acid as precursor of DES played key-role for effective metals separation. It was established that the solvent synthesized from choline chloride and malic acid provided highest extraction recovery (from 73 to 88%). Mixing and heating the solvent and sample for 30 min at a temperature of 70 °C provided effective separation of metals from plant sample. The developed procedure is not required a microwave digestion of samples. After separation the solvent phase containing analytes was dissolved in aqueous phase and analyzed. The developed procedure was applied to elemental analysis of plant tobacco and lettuce samples by inductively coupled plasma optical emission spectroscopy. Limits of detection calculated as three times the signal-to-noise ratio were in the range from 0.2 to 17 mg kg-1.

Reversed-phase dispersive liquid-liquid microextraction based on decomposition of deep eutectic solvent for the determination of lead and cadmium in vegetable oil.

In this work, a reversed-phase dispersive liquid-liquid microextraction procedure based on the decomposition of deep eutectic solvent was suggested for the first time. The procedure was utilized for fast and simple separation of lead and cadmium from vegetable oil samples. The procedure assumed mixing of oil sample and DES based on menthol, formic acid and water. Water as component of DES promoted its decomposition in sample matrix resulting menthol dissolution in the sample phase and dispersion of aqueous formic acid solution. In this procedure menthol acted as a dispersive solvent during DES decomposition for dispersion of aqueous formic acid solution. The metals were determined by the square-wave anodic stripping voltammetry. The limits of detection, were 0.01 µg kg-1 for lead and 0.006 µg kg-1 for cadmium. The RSD was less then 6% for both analytes. The enrichment factor was 36 and 39 for lead and cadmium, respectively.

Hydrolysis of triglycerides in milk to provide fatty acids as precursors in the formation of deep eutectic solvent for extraction of polycyclic aromatic hydrocarbons.

A microextraction pretreatment for powdered milk analysis, relying on the formation of a natural deep eutectic solvent is proposed. It relies on the in situ hydrolysis of milk fats (triglycerides) which yields fatty acids as precursors in the formation of the natural deep eutectic solvent. As a proof-of-concept, the innovation was applied to the determination of thirteen polycyclic aromatic hydrocarbons in powdered milk samples by HPLC with fluorometric detection. The alkaline hydrolysis of milk triglycerides minimized sample matrices interference through removal of proteins and fats, and led to formation of natural deep eutectic solvent precursors (fatty acids) directly from the sample components. Addition of only one precursor (terpenoid) was then required. Menthol and thymol (natural terpenoids) were investigated as deep eutectic solvent precursors for microextraction of polycyclic aromatic hydrocarbons. Under the selected experimental conditions, limits of detection were estimated within the 0.002-0.09 µg kg-1 range. The innovation provided satisfactory (70-91%) extraction of hydrophobic analytes from complex powdered milk matrices containing hydrophobic components (triglycerides) without the need for hazardous organic solvents. The RSD values were <5.2%.

Automated liquid-liquid microextraction and determination of sulfonamides in urine samples based on Schiff bases formation in natural deep eutectic solvent media.

In this work, an automated liquid-liquid microextraction procedure for the determination of sulfonamides (sulfamethoxazole, sulfamethazine and sulfapyridine) in urine samples using natural deep eutectic solvent is presented for the first time. The mechanism for extraction of sulfonamides was based on the formation of colored Schiff bases in the presence of vanillin, which acted as a derivatization reagent and precursor of natural deep eutectic solvent (an extractant). In this procedure, thymol was used as both media for Schiff bases formation and as a second precursor of the natural deep eutectic solvent. The formation of the Schiff bases was confirmed by mass spectrometry. A Lab-In-Syringe concept was applied for the automation of the microextraction procedure. The procedure involved mixing the sample and natural deep eutectic solvent into a syringe of a flow system, formation and microextraction of colored Schiff base followed by UV-Vis detection. Under optimal automated conditions the limits of detection, calculated from a blank test based on 3s (sigma) were 0.06, 0.1, and 0.06 mg L-1 for sulfapyridine, sulfamethoxazole and sulfamethazine. The proposed automated procedure permitted the routine determination of one drug (sulfamethoxazole, sulfamethazine or sulfapyridine) in urine samples to be achieved in less than 10 min.

Deep eutectic solvent decomposition-based microextraction for chromium determination in aqueous environments by atomic absorption spectrometry with electrothermal atomization.

A sensitive, rapid, and simple procedure for the determination of traces of chromium species in natural and waste waters after microextraction using a quasi-hydrophobic deep eutectic solvent based on tetrabutylammonium bromide and hexanoic acid was developed for the first time. In the developed procedure, the deep eutectic solvent played the role of a source of dispersive agent, chelating agent, and extraction solvent. During mixing the aqueous phase with the quasi-hydrophobic deep eutectic solvent, dissolution and dissociation of tetrabutylammonium bromide took place. Tetrabutylammonium bromide acted as a dispersive agent for the hexanoic acid emulsion formation and as an agent for the formation of an ion-association complex with Cr(vi) in an aqueous phase followed by its extraction in hexanoic acid. The organic phase containing Cr(vi) complexes was analyzed by atomic absorption spectrometry with electrothermal atomization. The enrichment factor value was 53, the extraction recovery was 89%, and the limit of detection calculated from a blank test, based on 3σ, was 5.0 ng L-1. The values of intra-day RSD and inter-day RSD were 3.9% and 5.0%, respectively.

Microstructured optical fibers sensor modified by deep eutectic solvent: Liquid-phase microextraction and detection in one analytical device.

A sensitive optical sensor based on hollow core microstructure optical fibers modified with deep eutectic solvent was produced for the first time. An easy procedure for the modification of hollow-core microstructure optical fibers with deep eutectic solvent was developed. Deep eutectic solvents based on natural monoterpenoids and fatty acids were investigated for glass surface modification. The sensor was used for the determination of non-steroidal anti-inflammatory drugs (mefenamic acid, diclofenac, flurbiprofen and ketoprofen) in human urine samples. The mechanism of the sensor response was investigated and discussed. Liquid-phase microextraction of non-steroidal anti-inflammatory drugs was implemented in deep eutectic solvent phase supported in the inner surface of hollow-core microstructure optical fibers followed by transmission spectra measurement in one analytical device. The preconcentration step performed directly in the analytical device allowed to obtain high sensitivity and selectivity. The limits of detection calculated from the calibration plots based on 3σ were 3 µg L-1 for all target analytes.

A synergistic effect of hydrophobic deep eutectic solvents based on terpenoids and carboxylic acids for tetracycline microextraction.

Hydrophobic deep eutectic solvents were investigated for tetracycline microextraction. It was found that a deep eutectic solvent consisting of thymol and octanoic acid provided a synergistic effect on tetracycline extraction. In this paper, a novel liquid-liquid microextraction procedure for the HPLC-DAD determination of tetracyclines in milk samples was proposed.

A rotating disk sorptive extraction based on hydrophilic deep eutectic solvent formation.

An elegant preconcentration method assumed sorption of polar analytes from complex non-polar matrices on a rotating disk based on hydrophilic deep eutectic solvent formation is presented for the first time. The surface of poly(vinylidene fluoride-co-tetrafluoroethylene) rotating disk was coated with choline chloride acted as a precursor of deep eutectic solvent (hydrogen bond acceptor). The rotating disk was immersed in vegetable oil sample and phenolic compounds (hydrogen bond donors) were efficient separated on the disk during its rotation due to deep eutectic solvent formation. Ability of hydrophilic deep eutectic solvent decomposition in aqueous phase was used for fast analytes elution from the disk surface (2 min). Finally, the obtained aqueous solution of phenolic compounds and choline chloride was analyzed by high-performance liquid chromatography with fluorescence detection. Under optimal conditions, the limits of detection for gallic acid, protocatechuic acid, tyrosol, vanillic acid, p-coumarinic acid, syringaldehyde and thymol were in the range of 10-60 µg L-1. The developed approach allowed to significantly reduce sorption and elution time in comparison with previously reported rotating disk sorptive extraction approaches. The extraction mechanism based on deep eutectic solvent formation provided selective separation of target analytes with absolute extraction recovery in the range of 66-87%.

Deep eutectic mixture membrane-based microextraction: HPLC-FLD determination of phenols in smoked food samples.

A novel approach for effective sample pretreatment of food was developed. This approach was based on in situ deep eutectic mixtures formation between analytes (hydrogen bond donors) and choline chloride (a hydrogen bond acceptor) supported in a hydrophilic porous membrane. By this action, the analytes were extracted and retained into the hydrophilic porous membrane. Finally, the hydrophilic porous membrane containing the analytes was transferred into an aqueous phase and back-extraction occurred due to deep eutectic mixture decomposition in the aqueous phase. The developed approach was applied to the HPLC-FLD determination of phenols (phenol, o-cresol, p-cresol, eugenol, isoeugenol and guaiacol) in smoked food samples. The limits of detection, calculated from a blank test based on 3σ, were 0.3 µg kg-1 for phenol, o-cresol, p-cresol; 0.6 µg kg-1 for eugenol, isoeugenol; and 1 µg kg-1 for guaiacol.

In-syringe dispersive liquid-liquid microextraction using deep eutectic solvent as disperser: Determination of chromium (VI) in beverages.

A novel approach for dispersive liquid-liquid microextraction based on the use of deep eutectic solvent as a disperser was presented for the first time. The procedure was automated based on an in-syringe flow system coupled with UV-Vis detection and demonstrated by the determination of chromium (VI) in beverages. This analytical task was used as a proof-of-concept example. The automated extraction procedure involved the aspiration of aqueous sample into a syringe pump with homogeneous mixture of extraction solvent (1-oсtanol) and deep eutectic solvent (tetrabutylammonium bromide - formic acid) containing color-forming reagent (1,5-diphenylcarbazide). This led to decomposition of deep eutectic solvent in aqueous phase resulting in dispersion of extraction solvent, oxidation of 1,5-diphenylcarbazide to 1,5- diphenylcarbazone in the presence of chromium (VI), and formation of colored chromium (III) complex with 1,5-diphenylcarbazone and its fast extraction. In this case composition of deep eutectic solvent played a key role for analyte extraction. Tetrabutylammonium bromide promoted mass transfer between aqueous phase and the extraction solvent droplets as a salting out agent, bromide ion acted as an ion-pare agent for analyte complex extraction, formic acid provided required pH value for analyte complex formation. Under the optimal conditions the limit of detection, calculated from a blank test based on 3s, was 0.2 µg L-1. The automated dispersive liquid-liquid microextraction using deep eutectic solvent as disperser can be considered as an available, efficient, rapid and environmentally friendly sample pretreatment approach.

Reversed-phase chromatomembrane extraction as a novel approach for automated sample pretreatment: Anions determination in biodiesel by ion chromatography with conductivity detection.

In this study, a reversed-phase chromatomembrane extraction (RP-CME) method as a novel approach for automated sample pretreatment was suggested for the first time. The RP-CME was applied to automated separation of anions (formate, chloride, nitrate, phosphate and sulfate) from biodiesel samples as a proof-of-concept example. The novel design of chromatomembrane cell was developed for on-line RP-CME. The RP-CME procedure assumed mass-transfer of water-soluble analytes from organic sample phase (biodiesel sample) to aqueous phase supported in a porous composite mass-transfer block. The composite mass-transfer block based on microporous hydrophobic poly (tetrafluoroethylene) and hydrophilic glass fiber was developed for the RP-CME implementation. The block provided the effective retention of aqueous phase into the cell and simultaneous penetration of organic phase. The hydrophilic membrane-based sheet was used for the on-line separation of hydrophilic emulsion (biodiesel in water) containing target analytes obtained during analytes elution by aqueous phase from the mass-transfer block. The RP-CME was successfully coupled with an ion chromatography with conductivity detection. The limits of detection, calculated from a blank test based on 3σ, were 5 µg kg-1 for sulfate, 6 µg kg-1 for nitrate, 3 µg kg-1 for chloride, 5 µg kg-1 for phosphate and 1 µg kg-1 for formate.

High rate laser deposition of conductive copper microstructures from deep eutectic solvents.

In this communication, the phenomenon of the laser chemical deposition of copper using deep eutectic solvents (DESs) on a dielectric substrate has been shown for the first time. The use of eutectic solvents made it possible to greatly simplify the procedure of metal deposition and increase the deposition rate by more than 150 times compared to the use of aqueous solutions.