Monitoring of some trace metals in honeys by flame atomic absorption spectrometry after ultrasound assisted-dispersive liquid liquid microextraction using natural deep eutectic solvent

Deep Eutectic Solvents for Extraction and Preconcentration of Organic and Inorganic Species in Water and Food Samples: A Review

Deep eutectic solvents (DESs) have been developed as green solvents and these are capable as alternatives to conventional solvents used for the extraction of organic and inorganic species from food and water samples. The continuous generation of contaminated waste and increasing concern for the human health and environment have compelled the scientific community to investigate more ecological schemes. In this concern, the use of DESs have developed in one of the chief approach in the field of chemistry. These solvents have appeared as a capable substitute to conventional hazardous solvents and ionic liquids. The DESs has distinctive properties, easy preparation and components availability. It is not only used in scienctific fields but also used in quotidian life. There are many advantages of DESs in analytical chemistry, they are largely used for extraction and determination of inorganic and organic compounds from different samples. In previous a few years, several advanced researches have been focused on the separation and preconcentration of low level of pollutants using DESs as the extractants. This review summarizes the use of DESs in the separation and preconcentration of organic and inorganic species from water and food samples using various microextraction processes.

Development of salt-induced homogeneous liquid-liquid extraction using a deep eutectic solvent performed in a narrow-bore tube for the extraction of Zn(II), Cu(II), and Cd(II) ions from honey samples

In this study, a sample preparation procedure based on salt-induced homogeneous liquid-liquid extraction performed in a narrow-bore tube was used for the preconcentration and extraction of Zn(II), Cu(II), and Cd(II) ions from honey samples. To perform the procedure, a mixture of working solution containing sodium chloride, acetonitrile, and a synthesized deep eutectic solvent (as an extraction solvent) was transferred into a narrow tube filled with solid sodium chloride up to a specific level. As the solution flowed through the tube, tiny droplets of the extraction solvent were formed at the boundary between the solution and salt layer. The droplets moved upwards in the tube and eventually collected as a distinct layer on the top of the solution. The separated phase was removed and dispersed into ionized water. After centrifugation, tiny droplets of the extraction solvent containing the analytes were sedimented at the bottom of the tube. The concentrated analytes were measured using flame atomic absorption spectrophotometry. The linear ranges and extraction recoveries were obtained in the ranges of 1.5-100 μg kg-1 and 89.6-94.8%, respectively. The detection limits ranged from 0.35 to 0.48 μg kg-1. Low relative standard deviations (C = 10 μg L-1, n = 6) of 3.1, 2.8, and 3.4% for Zn(II), Cu(II), and Cd(II), respectively, were obtained. Finally, the optimized method was successfully used in determination of concentration of the selected heavy metal ions in various honey samples.

Preconcentration of Heterocyclic Aromatic Amines in Edible Fried Insects Using Surfactant-Assisted Hydrophobic Deep Eutectic Solvent for Homogeneous Liquid-Liquid Microextraction prior to HPLC

Thermal processing techniques are often accompanied by the production of many harmful compounds such as heterocyclic aromatic amines (HAAs). To protect human health, an efficient and environmentally friendly method, namely, homogeneous liquid-liquid microextraction (HLLME), was investigated. This method is based on a surfactant-assisted hydrophobic deep eutectic solvent for the determination of HAAs in edible fried insect samples prior to their analysis by high-performance liquid chromatography coupled with UV detection. A hydrophobic deep eutectic solvent (as extraction solvent) was synthesized using decanoic acid as a hydrogen bond donor and tetrabutylammonium bromide (TBABr) as a hydrogen bond acceptor and then characterized by Fourier transform infrared (FTIR) spectroscopy. The surfactant was used as the emulsifier and induces mass transfer, resulting in an increasing extraction efficiency of the proposed method. Various factors affecting the extraction performance were investigated and optimized. A matrix-match calibration method was used to analyze HAAs in high heat-treated edible fried insect samples. Under optimized conditions, the proposed method showed good linearity (R2 ≥ 0.99) with satisfactory limits of detection and satisfactory reproducibility with relative standard deviation of less than 10.0%. Furthermore, the procedure greenness was assessed using the Analytical Eco-Scale. This paper represents the first application of HLLME based on a surfactant-assisted hydrophobic deep eutectic solvent to analyze HAAs in edible fried insect samples.

Trace-Level Determination of Triazole Fungicides Using Effervescence-Assisted Liquid-Liquid Microextraction Based on Ternary Deep Eutectic Solvent Prior to High-Performance Liquid Chromatography

A simple and sensitive preconcentration method, namely, effervescence-assisted liquid-liquid microextraction based on the ternary deep eutectic solvent method, was developed for enrichment of triazole fungicide residues prior to their determination by high-performance liquid chromatography coupled with UV detection. In this method, a ternary deep eutectic solvent (as extractant) was prepared by combination of octanoic acid, decanoic acid, and dodecanoic acid. The solution was well dispersed with sodium bicarbonate (as effervescence powder) without using auxiliary devices. In order to obtain relatively high extraction efficiency, analytical parameters were investigated and optimized. Under optimum conditions, the proposed method showed good linearity within the range of 1-1000 μg L^-1 with a coefficient for determination (R²) greater than 0.997. The low limits of detection (LODs) were in the range of 0.3-1.0 μg L^-1. The precisions were assessed from the relative standard deviations (RSDs) of retention time and peak area obtained from intra- (n = 3) and inter-day (n = 5 × 5) experiments, which were greater than 1.21 and 4.79%, respectively. Moreover, the proposed method provided high enrichment factors ranging from 112 to 142 folds. A matrix-match calibration method was used for analysis of real samples. Finally, the developed method was successfully applied for determination of the triazole fungicide in environmental water (near agricultural area), honey, and bean samples, and it represents a promising alternative method for analysis of triazoles. The recoveries of the studied triazoles were obtained in the range of 82-106% with an RSD less than 4.89.

Hydrophobic Deep Eutectic Solvents as Greener Substitutes for Conventional Extraction Media: Examples and Techniques

Deep eutectic solvents (DESs) are multicomponent designer solvents that exist as stable liquids over a wide range of temperatures. Over the last two decades, research has been dedicated to developing noncytotoxic, biodegradable, and biocompatible DESs to replace commercially available toxic organic solvents. However, most of the DESs formulated until now are hydrophilic and disintegrate via dissolution on coming in contact with the aqueous phase. To expand the repertoire of DESs as green solvents, hydrophobic DESs (HDESs) were prepared as an alternative. The hydrophobicity is a consequence of the constituents and can be modified according to the nature of the application. Due to their immiscibility, HDESs induce phase segregation in an aqueous solution and thus can be utilized as an extracting medium for a multitude of compounds. Here, we review literature reporting the usage of HDESs for the extraction of various organic compounds and metal ions from aqueous solutions and absorption of gases like CO₂. We also discuss the techniques currently employed in the extraction processes. We have delineated the limitations that might reduce the applicability of these solvents and also discussed examples of how DESs behave as reaction media. Our review presents the possibility of HDESs being used as substitutes for conventional organic solvents.

A simple and cost-effective synthesis route using itaconic acid to prepare a magnetic ion-imprinted polymer for preconcentration of Pb (II) from aqueous media

A new Pb (II) magnetic ion-imprinted polymer (Pb-MIIP) was successfully investigated for the selective extraction of Pb (II) from an aqueous solution. MIIP nanostructures were developed using itaconic acid-coated iron oxide nanoparticles (Fe₃O₄@ITA) as a novel magnetic core, ITA as a functional monomer and chelating agent, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and 2,2-azobisisobutyronitrile (AIBN) as an initiator. The triple application of ITA in the synthesis and reduction of the number of compounds in the preparation of the MIIP, in addition to being economical, reduces the possibility of side reactions. The synthesized products were followed and confirmed in each step by instrumental and microscopic methods. The limit of detection of the Pb (II)-MIIP method was 0.21 μg L^-1. Under the optimal conditions, the recovery (R%) was >90% with a relative standard deviation (RSD%) of <4.9%. The synthesized MIIP was reusable and successfully used to extract Pb (II) from tap water samples.

Relationships Linking the Element, Bioactive, Hydroxymethylfurfural, Color of Kars Honeys: a Chemometric Approach

Honey is a natural food substance considered among functional foods due to its positive effect on human health. Quality of honey is significantly influenced by environmental conditions and botanical origin. This study aimed to determine the element content in honey from Kars, Turkey, as well as the bioactive compounds and certain physicochemical and biochemical properties such as hydroxymethylfurfural (HMF) and color in a chemometric approach. In this study, a total of 41 local honey samples were analyzed. The levels of elements Al, As, B, Cd, Cr, Cu, Fe, Mg, Zn, and Pb were determined by inductively coupled plasma optical emission spectrophotometer (ICP-OES). The mean concentrations of the elements in the samples were identified as 3.09, 0.64, 59.07, 0.02, 0.14, 0.17, 1.76, 9.32, 0.78, and 0.33 µg/g for Al, As, B, Cd, Cr, Cu, Fe, Mg, Zn, and Pb, respectively. The mean bioactive compounds of the honey samples were determined as phenolic content (19.74 mg GAE/100 g), flavonoid content (4.47 mg CE/100 mg), and DPPH (49.08% inhibition). The HMF levels of all samples conformed to the honey standards of the Codex Alimentarius and Turkish Food Codex. HMF was not negatively correlated with the other color parameters except for the a* (redness or greenness) value. This study showed that clustering analysis (CA) and principal component analysis (PCA) are useful for distinguishing the originality of honey samples by using element content, bioactive properties, HMF, and color and were useful in defining the Kars honey type.

Concentration levels and an assessment of human health risk of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in honey and pollen

Persistent organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) accumulate in the food chain due to their physical and chemical properties and adversely affect human health. For this reason, this study aimed to determine the PAH and PCB concentration levels in pollen and honey samples in urban and semi-urban areas and to evaluate the risk of cancer that may occur by ingestion in Bursa, Turkey. The average total concentrations of 14 PAH (∑₁₄PAH) compounds in pollen and honey samples were found to be 304.3 ± 192.3 ng/g (average ± standard deviation) and 650.2 ± 118.1 ng/g for the urban area, and 329.6 ± 160.6 ng/g and 464.3 ± 66.4 ng/g for the semi-urban area, respectively. Similarly, ∑₁₄PCB concentrations in pollen and honey samples were found to be 8.7 ± 3.6 ng/g and 13.0 ± 4.8 ng/g for the urban area and 7.7 ± 2.2 ng/g and 17.4 ± 4.0 ng/g for the semi-urban area, respectively. It was determined that the pollen and honey samples in both sampling areas were affected by local PCB sources. The Pearson correlation coefficient (PCC) method determined the relationship between pollen and honey samples. According to the PCC values obtained, it was observed that pollen and honey in both sampling regions exhibited a significant relationship with each other. Finally, while there was no cancer risk for PCBs due to ingestion of honey and pollen in both sampling areas, acceptable cancer risk has been calculated for PAHs.

R. Rocha C, Teixeira JA, Pereira JAM. Green Extraction Techniques as Advanced Sample Preparation Approaches in Biological, Food, and Environmental Matrices: A Review

Green extraction techniques (GreETs) emerged in the last decade as greener and sustainable alternatives to classical sample preparation procedures aiming to improve the selectivity and sensitivity of analytical methods, simultaneously reducing the deleterious side effects of classical extraction techniques (CETs) for both the operator and the environment. The implementation of improved processes that overcome the main constraints of classical methods in terms of efficiency and ability to minimize or eliminate the use and generation of harmful substances will promote more efficient use of energy and resources in close association with the principles supporting the concept of green chemistry. The current review aims to update the state of the art of some cutting-edge GreETs developed and implemented in recent years focusing on the improvement of the main analytical features, practical aspects, and relevant applications in the biological, food, and environmental fields. Approaches to improve and accelerate the extraction efficiency and to lower solvent consumption, including sorbent-based techniques, such as solid-phase microextraction (SPME) and fabric-phase sorbent extraction (FPSE), and solvent-based techniques (μQuEChERS; micro quick, easy, cheap, effective, rugged, and safe), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), in addition to supercritical fluid extraction (SFE) and pressurized solvent extraction (PSE), are highlighted.

Use of green alternative solvents in dispersive liquid-liquid microextraction: A review

Dispersive liquid-liquid microextraction is one of the most widely used microextraction techniques currently in the analytical chemistry field, mainly due to its simplicity and rapidity. The operational mode of this approach has been constantly changing since its introduction, adapting to new trends and applications. Most of these changes are related to the nature of the solvent employed for the microextraction. From the classical halogenated solvents (e.g., chloroform or dichloromethane), different alternatives have been proposed in order to obtain safer and non-pollutants microextraction applications. In this sense, low-density solvents, such as alkanols, switchable hydrophobicity solvents, and ionic liquids were the first and most popular replacements for halogenated solvents, which provided similar or better results than these classical dispersive liquid-liquid microextraction solvents. However, despite the good performances obtained with low-density solvents and ionic liquids, researchers have continued investigating in order to obtain even greener solvents for dispersive liquid-liquid microextraction. For that reason, in this review, the evolution over the last five years of the three types of solvents already mentioned and two of the most promising solvent alternatives (i.e., deep eutectic solvents and supramolecular solvents), have been studied in detail with the purpose of discussing which one provides the greenest alternative.

Amine functionalized polyacrylonitrile fibers for the selective preconcentration of trace metals prior to their on-line determination by ICP-MS

Amine functionalized polyacrylonitrile fibers (PANFs) were prepared and applied for the simultaneous separation and preconcentration of V(v), As(iii), Sn(iv), Sb(iii) and Bi(ii) from environmental water samples in this paper. The functional PANFs were first prepared by nucleophilic substitution reaction between hydroxylamine hydrochloride and polyacrylonitrile fibers, and then the reactant obtained in the first step was subjected to a ring opening reaction with epichlorohydrin, followed by modification with triethylenetetramine (TETA). The structure of the final polymer fibers was analyzed by Fourier transform infrared spectroscopy (FT-IR), and the morphology was characterized by scanning electron microscopy (SEM). A home-made solid phase extraction (SPE) pretreatment column was filled with PANFs, and then online connected with inductively coupled plasma mass spectrometry (ICP-MS) for quantitative determination of metal ions. Under the optimized experimental conditions, the target metal ions were eluted rapidly and quantitatively using 0.3 mol L-1 HNO3 solution. Only with 30 mL sample solution, high enrichment factors of 120 were obtained for V(v), As(iii), Sn(iv) and Sb(iii), and 115 for Bi(ii), respectively. The detection limits achieved were low: 1.2, 0.9, 1.7, 1.5 and 2.3 ng L-1 for V(v), As(iii), Sn(iv), Sb(iii) and Bi(ii), respectively, and the relative standard deviations (RSDs) were below 3.0%. The advanced fiber materials prepared in this work have the advantages of low cost, environmental friendliness and high adsorption efficiency, and the on-line preconcentration method has greatly improved the analysis efficiency. Finally, the feasibility and accuracy of the method were validated by successfully analyzing Certified Reference Materials (CRMs) as well as lake, river and sea water samples.

[Progress in the application of deep eutectic solvents to extraction and separation technology]

With the rapid development of green chemistry, the design and application of the related methods and requisite solvents have received increasing attention in recent years. Deep eutectic solvents (DESs) are mixtures formed from a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD). Generally, ionic liquids (ILs) and DESs have similar physical and chemical properties, and hence, find application in the same fields. However, DESs have many advantages over ILs, such as non-toxicity, environmental friendliness, low cost, and biodegradability. Thus, there are many areas where DESs play a key role and act as new, efficient green extraction solvents. DESs can aid the extraction and separation of different target compounds from a variety of samples, thus promoting the rapid development of sample pretreatment technology. As extraction solvents, DESs offer unique advantages. In dispersive liquid-liquid microextraction (DLLME), DESs show incredible ability to extract residual drugs, metal ions, and bioactive components from complex matrices, which would require complicated sample preparation steps when using traditional organic extraction solvents. Compared with traditional organic extraction solvents, DESs have considerable merits of greenness, hypotoxicity, higher extraction efficiency, etc. Moreover, as a dispersant, a DES can accelerate the diffusion of the extractant in the sample solution during DLLME, owing to its benefits of miniaturization and low cost. Traditional dispersants such as methanol and acetonitrile have many disadvantages, including high volatility, flammability, and toxicity, while DESs are environmentally friendly. Therefore, the combination of DES and DLLME has recently gained prominence in the field of sample preparation. Additionally, the combination of DES and solid-phase extraction (SPE) has broad application prospects. By virtue of their diverse functions, DESs have been used as eluents, in combination with a solid-phase extraction column and a stir bar, to elute analytes from the sorbent surface. The molar ratio of the HBA and HBD is one of the important factors influencing the elution efficiency. DESs can be combined with magnetic multiwalled carbon nanotubes, magnetic graphene oxide, and other nanocomposites to specifically adsorb target analytes through hydrogen bonding, π-π forces, and electrostatic forces. In addition, the DES can be used in the synthesis of magnetic nanocomposites and molecularly imprinted polymers when combined with magnetic materials. Magnetic nanocomposites functionalized with DES show excellent performance and high efficiency in the extraction process. The combination of DES and magnetic materials would promote the development of magnetic materials for green chemistry and expand the application of DES to several other fields. However, to the best of our knowledge, research on the microstructure, physical and chemical properties, and extraction mechanism of DESs is still in its nascent stage. Therefore, exploring the theoretical mechanism and applications of new DESs with special functions would be an essential future research direction. This article integrates the research progress of DESs in extraction separation technology; introduces the preparation, properties, and classification of DESs; and summarizes the applications of DESs in DLLME and SPE.

Microextraction Techniques with Deep Eutectic Solvents

In this review, the ever-increasing use of deep eutectic solvents (DES) in microextraction techniques will be discussed, focusing on the reasons needed to replace conventional extraction techniques with greener approaches that follow the principles of green analytical chemistry. The properties of DES will be discussed, pinpointing their exceptional performance and analytical parameters, justifying their current extensive scientific interest. Finally, a variety of applications for commonly used microextraction techniques will be reported.

Deep Eutectic Solvents: A Review of Fundamentals and Applications

Deep eutectic solvents (DESs) are an emerging class of mixtures characterized by significant depressions in melting points compared to those of the neat constituent components. These materials are promising for applications as inexpensive "designer" solvents exhibiting a host of tunable physicochemical properties. A detailed review of the current literature reveals the lack of predictive understanding of the microscopic mechanisms that govern the structure-property relationships in this class of solvents. Complex hydrogen bonding is postulated as the root cause of their melting point depressions and physicochemical properties; to understand these hydrogen bonded networks, it is imperative to study these systems as dynamic entities using both simulations and experiments. This review emphasizes recent research efforts in order to elucidate the next steps needed to develop a fundamental framework needed for a deeper understanding of DESs. It covers recent developments in DES research, frames outstanding scientific questions, and identifies promising research thrusts aligned with the advancement of the field toward predictive models and fundamental understanding of these solvents.

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.

Recent Application of Deep Eutectic Solvents as Green Solvent in Dispersive Liquid-Liquid Microextraction of Trace Level Chemical Contaminants in Food and Water

As growing concerns on green, cost-effective, and time-saving chemistry analysis methods, deep eutectic solvents (DESs) are considered to be promising green alternatives to conventional solvents in dispersive liquid-liquid microextraction (DLLME) of trace level chemical contaminants in food and water, due to their biodegradability, low cost, and simple preparation. In the past few years, numerous innovative researches have focused on preconcentration of trace level chemical contaminants using DESs as extractant. In this context, this review aims to summarize the updated state-of-the-art effort dedicated to preconcentration of trace level chemical contaminants in food and water sample using DESs as extractants in DLLME. Furthermore, the major impact factors affecting the preconcentration efficiency and process mechanisms are thoroughly analyzed and discussed. Finally, prospects and challenges in application of DESs as solvents in DLLME to enrich trace level chemical contaminants are extensively elucidated and critically reviewed.

A sieve-conducted two-syringe-based pressurized liquid-phase microextraction for the determination of indium by slotted quartz tube-flame atomic absorption spectrometry

In this study, a new liquid-phase microextraction method termed sieve-conducted two-syringe-based pressurized liquid-phase microextraction (SCTS-PLPME) was developed as a preconcentration tool for indium. Here, two syringes were connected to each other by an apparatus to produce an environment subject to pressure. The pressure created between the two syringes by simultaneous movements of the syringe plungers (to and fro) generated an efficient dispersion and this eliminated the need for dispersive solvents. Determination of indium after preconcentration was carried out with a slotted quartz tube attached flame atomic absorption spectrometer (SQT-FAAS). The detection limit (LOD) and quantification limit (LOQ) of the developed method were calculated as 19.2 and 72.2 μg L^-1, respectively. The reliability and accuracy of the developed method was tested by performing recovery studies on lake water spiked at different concentrations and the obtained percent recoveries were between 101.2 and 106.9%.

Ligandless, deep eutectic solvent-based ultrasound-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase for preconcentration of lead, cadmium, cobalt and nickel in water samples

A green and efficient sample preparation method using a deep eutectic solvent-based ultrasounds-assisted dispersive liquid-liquid microextraction with solidification of the aqueous phase followed by high performance liquid chromatography analysis was developed for preconcentration and determination of heavy metals in environmental samples. In the proposed method, a novel, low density deep eutectic solvent was prepared by mixing trihexyl(tetradecyl)phosphonium chloride and thiosalicylic acid at a molar ratio of 1:2 and used both as an extractant and complexing agent. Ultrasound was used to disperse the extractant in the aqueous phase of the sample. Then, the phases were separated by centrifugation, after which the aqueous phase was frozen and the surface extractant phase was dissolved in a small volume of acetonitrile and subjected to liquid chromatographic analysis. The proposed method provided precisions (relative standard deviation, n = 5) in the range of 2.6-4.7%. The limit of detection were 0.05, 0.13, 0.06, and 0.11 µg/L for Pb(II), Cd(II), Co(II), Ni(II), respectively. The enhancement factors were equal to 154, 159, 162, and 158 for lead(II), cadmium(II), cobalt(II), and nickel(II), respectively. The accuracy of the proposed method was evaluated using certified reference materials (CA011b - hard drinking water, NIST 1643e - trace elements in water, TMRAIN-04 - simulated rain sample).