Ferrofluids based analytical extractions and evaluation of their greenness

Deep eutectic solvents with solid supports used in microextraction processes applied for endocrine-disrupting chemicals

The determination of endocrine-disrupting chemicals (EDCs) has become one of the biggest challenges in Analytical Chemistry. Due to the low concentration of these compounds in different kinds of samples, it becomes necessary to employ efficient sample preparation methods and sensitive measurement techniques to achieve low limits of detection. This issue becomes even more struggling when the principles of the Green Analytical Chemistry are added to the equation, since finding an efficient sample preparation method with low damaging properties for health and environment may become laborious. Recently, deep eutectic solvents (DESs) have been proposed as the most promising green kind of solvents, but also with excellent analytical properties due to the possibility of custom preparation with different components to modify their polarity, viscosity or aromaticity among others. However, conventional extraction techniques using DESs as extraction solvents may not be enough to overcome challenges in analysing trace levels of EDCs. In this sense, combination of DESs with solid supports could be seen as a potential solution to this issue allowing, in different ways, to determine lower concentrations of EDCs. In that aim, the main purpose of this review is the study of the different strategies with solid supports used along with DESs to perform the determination of EDCs, comparing their advantages and drawbacks against conventional DES-based extraction methods.

Hydroxyl-rich ferrofluid for efficient liquid phase microextraction of cinnamic acid derivatives in traditional Chinese medicine

In this study, a hydroxyl-rich ferrofluid was prepared by dispersing silica-coated magnetic nanoparticles into a methyltrioctylammonium chloride-glycerol deep eutectic solvent and then employed in the preconcentration of trace-level of cinnamic acid derivatives (caffeic acid, p-hydroxycinnamic acid, ferulic acid, and cinnamic acid) in traditional Chinese medicine prior to high-performance liquid chromatography analysis. The structures of the synthesized materials were characterized by X-ray diffraction and infrared spectroscopy. The experimental parameters affecting the extraction performance, such as deep eutectic solvent composition, dosage of ferrofluid, pH of aqueous sample solution, salt concentration, extraction time, type, and volume of desorption solvent, were studied and optimized. Under the optimum conditions, the enrichment factors of four cinnamic acid derivatives were in the range of 107-114. Low detection limits (0.2-0.9 ng/mL), good precisions (relative standard deviations 1.2%-9.5%), and satisfactory recoveries (96.0%-104.7%) were achieved. Subsequently, the possible microextraction mechanism of the proposed method was explored and elucidated. It showed that the prepared ferrofluid is easily dispersed in the aqueous sample and achieved recovery after the extraction. The developed approach is a simple, convenient, and efficient method for preconcentration and determination of cinnamic acid derivatives in complex matrices.

Determination of remdesivir in human plasma using (deep eutectic solvent-ionic liquid) ferrofluid microextraction combined with liquid chromatography

A microextraction technique based on ferrofluids was developed for the preconcentration and quantification of Remdesivir in human plasma samples. This method utilized a new type of magnetic colloids created by combining silica-coated magnetic particles with modified ionic liquid and natural hydrophobic deep eutectic solvent as the carrier liquid. The efficiency of the sorption and desorption steps was optimized using a chemometrics approach. Under the optimized conditions, the calibration curve exhibited linearity in the concentration range of 0.5 to 500.0 μg L-1, with a limit of detection and quantification of 0.2 and 0.5 μg L-1, respectively. The method precision was evaluated by assessing intra- and interday precision at three different analyte concentrations, yielding values of 8.9% and 16.8%, respectively. Moreover, the method accuracy fell within the range of 90.9% to 107.5%. This proposed method offers a green and environmentally friendly sample preparation technique for conducting pharmacodynamic, pharmacokinetic, and therapeutic drug monitoring studies of Remdesivir in biological fluids. Importantly, this technique eliminates the need for external energy sources or the use of dispersive solvents, providing a more efficient and sustainable approach.

Extraction of Organochlorine Pesticides from Porous Membrane Packed Dried Fish Samples: Method Development and Greenness Evaluation

In this work, ultrasound-assisted solvent extraction was utilized for extraction of organochlorine pesticides from membrane-protected dried fish samples. The dried fish samples were packed inside a porous membrane bag which was immersed in a solvent and subjected to ultrasonication. After the extraction process, the sample-containing bag was separated from the extract. Since samples were packed inside the membrane, their separation did not require centrifugation or filtration. Moreover, the complex components of the biota matrix may also retain inside the porous membrane bag, alleviating the requirement of extract cleanup before analysis. The parameters that can affect the ultrasound-assisted solvent extraction of membrane-protected dried fish samples were suitably optimized. These parameters include the extraction solvent and its volume, the sample amount, ultrasound intensity and extraction time. Under the optimum extraction conditions, good linearity was achieved for all the tested organochlorine pesticides, with the coefficients of determination (R2) higher than 0.9922 for the linear ranges from 5–1000, 10–1000 and 20–1000 ng/g. The values of intra-day and inter-day relative standard deviations were ≤13.8%. The limit of detection ranged from 1.5 to 6.8 ng/g. The spiked relative recoveries were in the range of 87.3–104.2%. This method demonstrated excellent figures of merit and could find potential applications in routine analytical laboratories. Finally, the greenness of this method was evaluated using the green analytical procedure index and analytical greenness calculator metrics.

Approaches on Ferrofluid Synthesis and Applications: Current Status and Future Perspectives

Ferrofluids are colloidal suspensions of iron oxide nanoparticles (IONPs) within aqueous or nonaqueous liquids that exhibit strong magnetic properties. These magnetic properties allow ferrofluids to be manipulated and controlled when exposed to magnetic fields. This review aims to provide the current scope and research opportunities regarding the methods of synthesis of nanoparticles, surfactants, and carrier liquids for ferrofluid production, along with the rheology and applications of ferrofluids within the fields of medicine, water treatment, and mechanical engineering. A ferrofluid is composed of IONPs, a surfactant that coats the magnetic IONPs to prevent agglomeration, and a carrier liquid that suspends the IONPs. Coprecipitation and thermal decomposition are the main methods used for the synthesis of IONPs. Despite the fact that thermal decomposition provides precise control on the nanoparticle size, coprecipitation is the most used method, even when the oxidation of iron can occur. This oxidation alters the ratio of maghemite/magnetite, influencing the magnetic properties of ferrofluids. Strategies to overcome iron oxidation have been proposed, such as the use of an inert atmosphere, adjusting the Fe(II) and Fe(III) ratio to 1:2, and the exploration of other metals with the oxidation state +2. Surfactants and carrier liquids are chosen according to the ferrofluid application to ensure stability. Hence, a compatible carrier liquid (polar or nonpolar) is selected, and then, a surfactant, mainly a polymer, is embedded in the IONPs, providing a steric barrier. Due to the variety of surfactants and carrier liquids, the rheological properties of ferrofluids are an important response variable evaluated when synthesizing ferrofluids. There are many reported applications of ferrofluids, including biosensing, medical imaging, medicinal therapy, magnetic nanoemulsions, and magnetic impedance. Other applications include water treatment, energy harvesting and transfer, and vibration control. To progress from synthesis to applications, research is still ongoing to ensure control of the ferrofluids' properties.