Investigation of tetrabutylammonium bromide-glycerol-based deep eutectic solvents and their mixtures with water by spectroscopic techniques

Spectrophotometric determination for green hydrophobic deep eutectic solvent-based microextraction of Brilliant Blue FCF (E133) from beverages

In this study, a simple, sensitive, and rapid method called green hydrophobic deep eutectic solvent-based liquid-liquid microextraction was developed to extract Brilliant Blue FCF dye from beverages. This method utilizes hydrophobic DES obtained by forming tetrabutylammonium bromide and 1-octanol in a 1:5 ratio as green extraction solvent. The transition of Brilliant Blue FCF to the DES phase occurred on its own, without the need for any reagents such as added salt or tetrahydrofuran. Several crucial factors were tried to get the best extraction efficiency, including species, DES volume and molar ratio, solution pH, ultrasonication, and centrifugation time. Under optimum conditions, extraction recoveries were achieved in the range of 95.1-101.3 % with the method developed for Brilliant Blue FCF. The detection and determination limits were observed to be 4.1 μg l-1 and 12.1 μg l-1, respectively. In addition, the relative standard deviation values for the method's accuracy were found to be 2.23 % and 3.48 % within and between days, respectively. It has been established that the developed method is highly environmentally friendly thanks to the application of the Analytical GREENness (AGREE) and Green Analytical Procedure Index (GAPI) tools. This study shows that DES applications can be carried out without the use of emulsifiers and dispersants by prioritizing the use of hydrophobic DES compounds as environmentally friendly and green extraction solvents in food samples.

Combined experimental and computational investigation of tetrabutylammonium bromide-carboxylic acid-based deep eutectic solvents

Aiming at shedding light on the molecular interactions in deep eutectic solvents (DESs), the DESs based on tetrabutylammonium bromide (TBAB) as hydrogen bond acceptor (HBA) and carboxylic acids (CAs) (formic acid (FA), oxalic acid (OA), and malonic acid (MA)) as hydrogen bond donor (HBD) were investigated by both experimental and theoretical techniques. The thermal behaviors of the prepared DESs were investigated by differential scanning calorimetry (DSC) method. In order to study the hydrogen bond formation between the DESs constituents, the FT-IR analysis was carried out. The large positive deviations of the iso solvent activity lines of ternary HBA + HBD + 2-propanol mixtures determined by the isopiestic technique from the semi-ideal behavior indicate that CAs interact strongly with TBAB and therefore they can form DESs. Molecular dynamics (MD) simulations were performed to present an atomic-scale image of the components and describe the microstructure of DESs. From the MD simulations, the radial distribution functions (RDFs), coordination numbers (CNs), combined distribution functions (CDFs), and spatial distribution functions (SDFs) were calculated to investigate the interaction between the components and three-dimensional visualization of the DESs. The obtained results confirmed the importance of hydrogen bonds in the formation of TBAB/CAs DESs.

An Innovative Vortex-Assisted Liquid-Liquid Microextraction Approach Using Deep Eutectic Solvent: Application for the Spectrofluorometric Determination of Rhodamine B in Water, Food and Cosmetic Samples

A new green and highly sensitive method for the determination of rhodamine B (RhB) by deep eutectic solvent-based vortex-assisted liquid-liquid microextraction with fluorescence detection (DES-VALLME-FLD) was developed. The extraction efficiency of conventional solvents and different deep eutectic solvent (DES) systems composed of tetrabutylammonium bromide (TBAB) and an alcohol (hexanol, octanol, or decanol) in different ratios were compared. DFT calculations of intermolecular electrostatic and non-covalent interactions of the most stable RhB forms with DES and water explain the experimental DESs' extraction efficiency. Semiempirical PM7 computations were used to obtain Hansen solubility parameters, which supported the good solubility of the monocationic RhB form in selected DESs. The dependence of the linear calibration of microextraction into 100 µL DES was observed in the RhB calibration range from 0.2 to 10.0 µg L-1 with a correlation coefficient of R2 = 0.9991. The LOD value was calculated to be 0.023 µg L-1. The accuracy and precision of the proposed method were verified over two days with RSD values of 2.9 to 4.1% and recovery of 94.6 to 103.7%. The developed method was applied to the determination of RhB in real samples (tap water, energy drink, and lipstick).

Water Induced Alterations in Self-Assembly of a Bio-Surfactant in Deep Eutectic Solvent for Enhanced Enzyme Activity

Deep eutectic solvents (DESs) meet important requirements for green solvent technology, including non-toxicity, biodegradability, sustainability, and affordability. Despite possessing low cohesive energy density than water, DESs have been found to support the self-assembly of amphiphiles. It is very much pertinent to examine the effect of water on self-assembly of surfactants in DESs as the presence of water alters the inherent structure of DES, which is expected to affect the characteristic properties of self-assembly. Following this, we have investigated the self-assembly of amino-acid based surfactant, Sodium N-lauroyl sarcosinate (SLS), in DES-water mixtures (10, 30 and 50 w/w% of water) and explored the catalytic activity of Cytochrome-c (Cyt-c) in the formed colloidal systems. Investigations using surface tension, fluorescence, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC) have shown that DES-water mixtures promote the aggregation of SLS, resulting in the lower critical aggregation concentration (cac ∼1.5-6-fold) of the surfactant as compared to water. The nanoclustering of DES at low water content and it's complete de-structuring at high water content affects the self-assembly in a contrasting manner governed by different set of interactions. Further, Cyt-c dispersed in DES-water colloidal solutions demonstrated 5-fold higher peroxidase activity than that observed in phosphate buffer.

Hydrophilic and hydrophobic deep eutectic solvent-based extraction to determine parathion in cereals by digital image colorimetry integrated with smartphones

To determine parathion in cereals, hydrophilic and hydrophobic deep eutectic solvents (DESs) were used by digital image colorimetry with smartphones. In the solid-liquid extraction part, hydrophilic DESs were used as extractants to extract parathion from cereals. In the liquid-liquid microextraction part, hydrophobic DESs dissociated into terpineol and tetrabutylammonium bromide in situ. The dissociated hydrophilic tetrabutylammonium ions reacted with parathion extracted in hydrophilic DESs under alkaline conditions to produce a yellow product, which was extracted and concentrated by dispersed organic phase terpinol. Digital image colorimetry integrated with the use of a smartphone was used for quantitative analysis. The limit of detection and quantification were 0.003 mg kg^-1 and 0.01 mg kg^-1, respectively. The recoveries for parathion were 94.8-106.2% with a relative standard deviation less than 3.6%. The proposed method was applied to analyze parathion in cereal samples: the method has the potential to be applied to pesticide residue analysis in food products.

VOCs absorption from gas streams using deep eutectic solvents - A review

Volatile organic compounds (VOCs) are one of the most severe atmospheric pollutants. They are mainly emitted into the atmosphere from anthropogenic sources such as automobile exhaust, incomplete fuel combustion, and various industrial processes. VOCs not only cause hazards to human health or the environment but also adversely affect industrial installation components due to their specific properties, i.e., corrosive and reactivity. Therefore, much attention is being paid to developing new methods for capturing VOCs from gaseous streams, i.e., air, process streams, waste streams, or gaseous fuels. Among the available technologies, absorption based on deep eutectic solvents (DES) is widely studied as a green alternative to other commercial processes. This literature review presents a critical summary of the achievements in capturing individual VOCs using DES. The types of used DES and their physicochemical properties affecting absorption efficiency, available methods for evaluating the effectiveness of new technologies, and the possibility of regeneration of DES are described. In addition, critical comments on the new gas purification methods and future perspectives are included.

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.

Copper-Free Halodediazoniation of Arenediazonium Tetrafluoroborates in Deep Eutectic Solvents-like Mixtures

Deep Eutectic Solvent (DES)-like mixtures, based on glycerol and different halide organic and inorganic salts, are successfully exploited as new media in copper-free halodediazoniation of arenediazonium salts. The reactions are carried out in absence of metal-based catalysts, at room temperature and in a short time. Pure target products are obtained without the need for chromatographic separation. The solvents are fully characterized, and a computational study is presented aiming to understand the reaction mechanism.