Emulsification liquid–liquid micro-extraction based on natural deep eutectic solvent for (triarylmethane) dyes determination

Exploration of supramolecular solvent-based microextraction for crystal violet detecting in water samples

This approach highlights the advantages of supramolecular solvents in a new microextraction model. The distinct properties and behavior of this supramolecular solvent provide enhanced extraction capabilities for detecting crystal violet (CV) in water samples. The methodical experimentation was executed to optimize the critical process parameters, providing maximum efficiency of crystal violet extraction at optimal conditions with pH set at 2.7, 186 μL of extraction solvent, extraction time of 3.5 min, and a salt amount of 3.1 % w/v, yielding the best results. Analytical data from extraction experiments under these optimal conditions demonstrated a high extraction percentage. The extraction model exhibited a linear response within the range of 10-800 ng mL-1 of crystal violet, with a detection limit of 2 ng mL-1. This model enables the measurement of CV in water samples with recovery rates exceeding 97 %, offering a straightforward and accessible approach for analysis.

Testing Thymol-Based DES for the Elimination of 11 Textile Dyes from Water

Textile industries release dangerous wastewater that contain dyes into the environment. Due to their toxic, carcinogenic and mutagenic nature, they must be removed before the discharge. Liquid–liquid extraction has proven to be an efficient method for the removal of these dyes. As extractants, deep eutectic solvents (DESs) have shown excellent results in recent years, as well as presenting several green properties. Therefore, four different hydrophobic DESs based on natural components were prepared thymol:decanoic acid (T:D (1:1)), thymol:DL-menthol (T:M (1:1)), thymol:DL-menthol (T:M (1:2)) and thymol:coumarin (T:C (2:1)) for the extraction of Malachite Green (MG), Brilliant Blue G (BBG), Acid Yellow 73 (AY73), Reactive Red 29 (RR29), Acid Blue 113 (AB113), Reactive Black 5 (RB5), Remazol Brilliant Blue (RBB), Direct Yellow 27 (DY27), Acid Blue 80 (AB80), Direct Blue 15 (DB15) and Acid Violet 43 (AV43) dyes from water. The operational parameters of the liquid–liquid extraction were selected in order to save time and materials, resulting in 30 min of stirring, 15 min of centrifugation and an aqueous:organic ratio of 5:1. In these conditions, the highest values of extraction obtained were 99% for MG, 89% for BBG and 94% for AY73. Based on these results, the influence of the aqueous:organic phase ratio and the number of necessary stages to achieve water decolorization was studied.

Efficient Extraction of Methylene Blue from Aqueous Solution Using Phosphine-Based Deep Eutectic Solvents with Carboxylic Acid

Methylene blue (MB), an organic thiazine dye, has numerous industrial and medical applications. However, MB is a wastewater contaminant that is harmful to humans and aquatic life. Hence, its removal from water bodies is essential. In this work, five novel deep eutectic solvents (DESs) were synthesized using different precursors, screened, and studied for the extraction of methylene blue (MB) from aqueous solution using liquid–liquid extraction. The first, TOP-SA, was synthesized using trioctylphosphine (TOP) as a hydrogen bond acceptor (HBA) and 2-hydroxy benzoic acid as a hydrogen bond donor (HBD). Among these, TOP-SA had the highest MB removal efficiency. The effects of pH, contact time, initial MB concentration, volumetric ratio, temperature, and ionic strength were studied and optimized. A 99.3% removal was achieved in 5 min for a 200 mg dm−3 MB solution mixed in a 1:10 ratio with TOP-SA at 25.0 °C. The structural properties of TOP-SA and its interactions with MB were investigated using FTIR. TOP-SA’s toxicity was investigated using human cells in vitro. TOP-SA was found to be comparatively less toxic and is a more efficient MB remover than other literature reported ionic liquids (ILs).

A Critical Review of Emerging Hydrophobic Deep Eutectic Solvents' Applications in Food Chemistry: Trends and Opportunities

Due to their low cost, biodegradability, and ease of preparation, deep eutectic solvents (DESs) are considered promising green alternatives to conventional solvents, as exploiting green solvents has been a research focus for achieving sustainable development goals. Most DESs in published studies are hydrophilic. On the other hand, the DES's hydrophilicity restricts its practical applicability to just polar molecules, which is a vital disadvantage to this extractant. Hydrophobic DES (HDES) has been developed as a new extractant adept at extracting nonpolar inorganic and organic compounds from aqueous systems. Although there has been little research on HDESs (HDES publications account for <10% of DES), specific intriguing applications have been discovered, requiring investigation and comparisons. As a result, this review covers the applications of emerging HDES in detecting pesticide residues, food additives, contaminants in food packaging, heavy metals, separation and extraction processes in food. According to the available literature, HDESs have the potential to overcome the limitations of hydrophilic DESs and be used in a broader range of applications in food with greater efficiency, which has received little attention. HDES is expected to substitute a lot of harmful organic extractants used for analytical reasons (food chemistry) in the future. Besides, the limitations of HDES were reviewed, and future studies were provided. This will serve as a reference for green chemistry advocates and practitioners in food science who want to minimize pollution and improve efficiency and benefit from the further development of HDESs.

Pressurized natural deep eutectic solvents: An alternative approach to agro-soy by-products

Soybeans are mainly used for food and biodiesel production. It is estimated that soy crops worldwide will leave about 651 million metric tons of branches, leaves, pods, and roots on the ground post-harvesting in 2022/23. These by-products might serve as largely available and cheap source of high added-value metabolites, such as flavonoids, isoflavonoids, and other phenolic compounds. This work aimed to explore green approaches based on the use of pressurized and gas expanded-liquid extraction combined with natural deep eutectic solvents (NADESs) to achieve phenolic-rich extracts from soy by-products. The total phenolic and flavonoid contents of the generated extracts were quantified and compared with conventional solvents and techniques. Pressurized liquid extraction (PLE) with choline chloride/citric acid/water (1:1:11 – molar ratio) at 120°C, 100 bar, and 20 min, resulted in an optimized condition to generate phenolic and flavonoid-rich fractions of soy by-products. The individual parts of soy were extracted under these conditions, with their metabolic profile obtained by UHPLC-ESI-QToF-MS/MS and potential antioxidant properties by ROS scavenging capacity. Extracts of soy roots presented the highest antioxidant capacity (207.48 ± 40.23 mg AA/g), three times higher than soybean extracts (68.96 ± 12.30). Furthermore, Hansen solubility parameters (HSPs) were applied to select natural hydrophobic deep eutectic solvents (NaHDES) as substituents for n-heptane to defat soybeans. Extractions applying NaHDES candidates achieved a similar yield and chromatography profile (GC-QToF-MS) to n-heptane extracts.

Polysaccharide-based substrate for surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) became a useful analytical technique with the development of appropriate metallic substrates. The need for SERS substrates that immobilize metallic nanoparticles prompted this work to search for an appropriate material. This work presents the preparation, characterization and application of a SERS substrate for crystal violet (CV) detection, as the probe molecule. The inner layer of the substrate is a thin film of the fungal β-D-glucan, botryosphaeran, covered by a thin layer of silver nanoparticles (AgNPs). The nanoparticles were produced by laser ablation, a fast and clean method for their preparation, and the layers were assembled by casting. Scanning electron and atomic force microscopies, UV-VIS and Raman spectroscopy and X-ray diffraction allowed the characterization of the surface of the substrate. Analysis by Raman spectroscopy showed promising results for SERS amplification on the substrate. Detection of CV reached enhancement factors up to 10⁶ orders of magnitude, compared to normal Raman spectra. Linearity was observed for analyses on the SERS substrate at concentration ranges of 0.005 to 1 µmol L^-1. The assembly reached the detection of 12 pmol cm^-2 of CV, which corresponds to 96 fg of the probe molecule contained in the area of the substrate effectively interacting with the laser. The substrate was more efficient than silver colloids to perform SERS.

A Review of the Use of Eutectic Solvents, Terpenes and Terpenoids in Liquid–liquid Extraction Processes

Diverse and abundant applications of the eutectic solvents have appeared in the last years. Their promising tunable properties, eco-friendly character and the possibility of being prepared from numerous compounds have led to the publication of numerous papers addressing their use in different areas. Terpenes and terpenoids have been employed in the formulation of eutectic solvents, though they also have been applied as solvents in extraction processes. For their hydrophobic nature, renewable character, low environmental impact, cost and being non-hazardous, they have also been proposed as possible substitutes of conventional solvents in the separation of organic compounds from aqueous streams, similarly to hydrophobic eutectic solvents. The present work reviews the application of eutectic solvents in liquid–liquid extraction and terpenes and terpenoids in extraction processes. It has been made a research in the current state-of-the-art in these fields, describing the proposed applications of the solvents. It has been highlighted the scale-up feasibility, solvent regeneration and reuse procedures and the comparison of the performance of eutectic solvents, terpenes and terpenoids in extraction with conventional organic solvents or ionic liquids. Ultimately, it has been also discussed the employ of predictive methods in extraction, the reliability of thermodynamic models in correlation of liquid–liquid equilibria and simulation of liquid–liquid extraction processes.