Solid-phase extraction followed by deep eutectic solvent based dispersive liquid–liquid microextraction and GC-MS detection of the estrogenic compounds in wastewater samples

Microextraction techniques with deep eutectic solvents for gas chromatographic analysis: a minireview

Sample pretreatment is one of the key steps in sample analysis. The design and development of new materials promote advancements in sample pretreatment technology. Deep eutectic solvents (DESs) are a novel material that have been developed in recent years. They possess characteristics such as low toxicity, good thermal stability, simple preparation methods, and low cost. DESs have the potential to replace traditional organic extraction solvents. DESs are formed from a hydrogen bond donor (HBD) and acceptor (HBA). Changing the type of HBA and HBD or their ratio leads to variations in the structure and properties of the resulting DESs. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) are the primary analytical techniques used in laboratories. This paper analyzes the selection relationship between DESs and analytes, as well as the steps of sample pretreatment, based on the characteristics of GC instruments, and utilizing DES extractants and extraction materials for sample pretreatment. This paper summarizes the progress of DES-based microextraction methods for GC. It introduces the different classifications of liquid and solid-phase microextraction and the application of DESs in them. The theoretical mechanism and extraction/separation mechanism of DESs are analyzed, and potential application of DESs in extraction/separation technology is discussed.

Deep eutectic solvents for the extraction of polyphenols from food plants

Deep Eutectic Solvents (DESs) offer a promising, sustainable alternative for extracting polyphenols from food plants, known for their health benefits. Traditional extraction methods are often costly and involve toxic solvents. This review discusses the basic concepts, preparation techniques, and factors influencing the effective and safe use of DESs in polyphenol extraction. DESs' adaptability allows integration with other green extraction technologies, such as microwave- and ultrasound-assisted extractions, enhancing their efficiency. This adaptability demonstrates the potential of DESs in the sustainable extraction of bioactive compounds. Current research indicates that DESs could play a significant role in the sustainable procurement of these compounds, marking an important advancement in food science research and development. The review underscores DESs as a realistic, eco-friendly alternative in the realm of natural extraction technologies, offering a significant contribution to sustainable practices in food science.

Membrane-protected magnetic covalent organic framework for efficient extraction of estrogens in dairy products

The presence of estrogens residues in dairy products is a growing concern due to their potential health risk. Herein, in this study, we have developed a membrane-protected magnetic solid-phase extraction (MP-MSPE) method that utilized a magnetic adsorbent (Fe3O4@COF-LZU1) with in-situ growth for the efficient extraction of estrone (E1), 17β-estradiol (E2), and estriol (E3). When combined with HPLC-FLD, this method allows for the efficient detection of estrogens in dairy products. The stability of the MP-MSPE was improved by the presence of a dialysis membrane, which remained a high extraction efficiency (90 %) even after ten reuse cycles. The hydrogen bonding, π-π interactions and pore size effect contribute to the excellent adsorption of three estrogens onto Fe3O4@COF-LZU1. Under optimal conditions, the method exhibits a low detection limit (0.01-0.15 μg L-1), wide linear range (0.1-800 μg L-1), and favorable recoveries (77.3 %-109.4 %) at three concentration levels (10, 50 and 100 μg L-1). This proposed method is characterized by its simplicity, high efficiency and eco-friendliness, making it a promising approach for extracting estrogens from dairy products.

Deep eutectic solvents for the determination of endocrine disrupting chemicals

The harmful effects of endocrine disrupting chemicals (EDCs) to humans and other organisms in the environment have been well established over the years, and more studies are ongoing to classify other chemicals that have the potential to alter or disrupt the regular function of the endocrine system. In addition to toxicological studies, analytical detection systems are progressively being improved to facilitate accurate determination of EDCs in biological, environmental and food samples. Recent microextraction methods have focused on the use of green chemicals that are safe for analytical applications, and present very low or no toxicity upon disposal. Deep eutectic solvents (DESs) have emerged as one of the viable alternatives to the conventional hazardous solvents, and their unique properties make them very useful in different applications. Notably, the use of renewable sources to prepare DESs leads to highly biodegradable products that mitigate negative ecological impacts. This review presents an overview of both organic and inorganic EDCs and their ramifications on human health. It also presents the fundamental principles of liquid phase and solid phase microextraction methods, and gives a comprehensive account of the use of DESs for the determination of EDCs in various samples.

Hydrophobic Natural Eutectic Solvents for the Gas Chromatographic Determination of Suspected Allergens in Fragrances by Dispersive Liquid-Liquid Microextraction

The fragrance industry plays a key role in the global economy, producing a wide range of personal care and household products. However, some fragrance ingredients have been linked to allergic reactions in sensitive people, and their concentrations are regulated at the European level. For this reason, reliable, rapid, and sustainable analytical methods are needed to rapidly detect and quantify these compounds. Recently, a new class of hydrophobic eutectic solvents (HES) has been introduced; they consist of natural terpenoids or phenolic compounds that can be used as hydrogen bond donors (HBD) and acceptors (HBA), and they are more suitable for GC applications due to their higher volatility. In this study, a dispersive liquid–liquid microextraction (DLLME) approach is proposed for the analysis and quantification of a range of allergens in hydroalcoholic perfumes. The optimized method requires only 50 µL of a natural HES (thymol–eugenol), which is readily dispersed by vortexing in 2 mL of sample. After centrifugation, the HES rich phase is diluted in 400 µL EtOH and directly injected into the GC-FID system. The proposed method has been successfully applied in the analysis and quantification of commercial fragrances, demonstrating good enrichment of target allergens and suitability for aqueous matrices analysis.

Highly sensitive and group-targeting detection of steroid estrogens in water environment using a valid oligonucleotide class-specific editing technique

Steroid environmental estrogens (SEEs) are often coexist in water, require complex analytical techniques for separation and monitoring. However, aptamer-based chemical detection often only recognizes one of them, and the detection of SEEs is still a huge challenge. Herein, a group-targeting aptamer with the ability to recognize SEEs was constructed using efficient oligonucleotide class-specific editing technology, and a photoelectrochemical aptasensor capable of detecting the class of SEEs was established. A quantitative analysis of highly toxic SEEs in the environment and carrying similar core carbon skeleton, including 17β-estradiol, esterone, estriol and ethinylestradiol, was performed. The detection limit was as low as 0.1 nM with a response time of only 15 min. Specifically, this method exhibited high anti-interference with different complex media existing. Combining the theoretical calculations with a variety of spectral experiments, the Π-Π stacking and hydrogen bond synergistic interactions between the photoelectric interface and the three ring structures on SEEs and the hydroxyl group of ring 1 were analyzed in depth. Besides, the conformational changes of loose base helix structure and the free rotation limitation of oligonucleotides after the recognition of SEEs at the molecular level were also elucidated, facilitating the transfer of electrons on the surface of the photoelectrode.

Novel deep eutectic solvent-based liquid phase microextraction for the extraction of estrogenic compounds from environmental samples

Steroid hormones, such as estrone (E1), 17β-estradiol (E2), 17β-ethinylestradiol (EE2) and estriol (E3) are a group of lipophilic active substances, synthesized biologically from cholesterol or chemically. A pH-switchable hydrophobic deep eutectic solvent-based liquid phase microextraction (DES-LPME) technique was established and combined with gas chromatography-mass spectroscopy for the determination of estrogenic compounds in environmental water and wastewater samples. A DES was synthesized using l-menthol as HBA and (1S)-(+)-camphor-10-sulfonic acid (CSA) as HBD, and used as a green extraction solvent. By adjusting the pH of the solution, the unique behavior of the DES in the phase transition and extraction of the desired analytes was investigated. The homogenization process of the mixture is done only by manual shaking in less than 30 seconds and the phase separation is done only by changing the pH and without centrifugation. Some effective parameters on the extraction and derivatization, such as molar ratio of DES components, DES volume, KOH concentration, HCl volume, salt addition, extraction and derivatization time and derivatization prior or after extraction were studied and optimized. Under the optimum conditions, relative standard deviation (RSD) values for intra-day and inter-day of the method based on 7 replicate measurements of 20 ng L⁻¹ of estrogenic compounds and 10 ng L⁻¹ for internal standard in different samples were in the range of 2.2–4.6% and 3.9–5.7%, respectively. The calibration graphs were linear in the range of 0.5–100 ng L⁻¹ and the limits of detection (LODs) were in the range of 0.2–1.0 ng L⁻¹. The relative recoveries of environmental water and wastewater samples which have been spiked with different levels of target compounds were 91.0–108.8%.

A pH-switchable hydrophobic deep eutectic solvent-based liquid phase microextraction (DES-LPME) technique was established and combined with gas chromatography–mass spectroscopy for the determination of estrogenic compounds in environmental samples.

Strategies of dispersive liquid-liquid microextraction for coastal zone environmental pollutant determination

Coastal zone means the interface of land and sea, and therefore, environmental pollutants steaming from land-based activities (like manufactories) and sea-based activities (like shipping) are all existing in coastal zone. These pollutants usually have characteristics of low residues, complicated matrices, easy accumulation and so on, causing difficulty to detect coastal pollutants quickly and sensitively. It is imperative to perform effective sample preparation prior to instrumental analysis. Dispersive liquid-liquid microextraction (DLLME) has attracted significant research interest for sample preparation, owing to its high enrichment ability, low reagent/sample consumption, and wide analyte/matrix applicability, as well as robustness, simplicity, rapidity and inexpensiveness. Herein, we comprehensively review the recent advancements of DLLME technology and its analytical parameters including enrichment principles, extraction modes, and practical application; the emphasis is on novel mode-construction and representative coastal-environmental pollutants extraction. Construction strategies are highlighted by classifying DLLME into five major modes, according to extractant's types, including normal ones, low density solvents, ionic liquids, deep eutectic solvents and others. The coupling of DLLME with other extraction techniques like solid-phase extraction is also briefly introduced. The strengths and weaknesses of each strategy and its rationality are also elaborated. In addition, some typical applications of the different DLLME modes for the determination of organic compounds and heavy metals in coastal water, sediment, soil, and biota are summarized. The increasingly concerned green aspects and instrumentation of DLLME are presented, and finally, the challenges and perspectives of the DLLME for environmental analysis are proposed.

Recognition and Selectivity Analysis Monitoring of Multicomponent Steroid Estrogen Mixtures in Complex Systems Using a Group-Targeting Environmental Sensor

The same class of steroid estrogen mixtures, coexisting in the environment of 17β-estradiol, estrone (E1), and ethinyl estradiol (EE2), have strong ability to disrupt the human endocrine system and are seriously prejudicial to the health of the organism and environmental safety. Herein, a highly sensitive and group-targeting environmental monitoring sensor was fabricated for a comprehensive analysis of multicomponent steroid estrogens (multi-SEs) in complex systems. This breakthrough was based on the highly sensitive photoelectrochemical response composite material CdSe NPs-TiO₂ nanotube and highly group-specific aptamers. The optimized procedure exhibited not only high sensitivity in a wide range of concentrations from 0.1 to 50 nM, indeed, the minimum detection limit was 33 pM, but also strong resistance to interference. The affinity and consistent action pockets of this sensor enable selective detection of multi-SEs in complex systems. It subsequently was applied for the analysis of multi-SEs from three real samples in the environment including medical wastewater, river water, and tap water to provide a means to clarify the fate of multi-SEs in the process of migration and transformation. This monitoring sensor has a brilliant application prospect for the identification and monitoring of the same class of endocrine-disrupting chemical mixtures in environmental complex systems.

Extraction and determination of strobilurin fungicides residues in apple samples using ultrasound-assisted dispersive liquid-liquid microextraction based on a novel hydrophobic deep eutectic solvent followed by H.P.L.C-U.V

In this study, several novel and natural hydrophobic deep eutectic solvents (D.E.Ss) were prepared using methyl trioctylammonium chloride (M.T.O.A.C) as H.B.A and different types of straight chain alcohols as H.B.Ds. One of the D.E.Ss composed of M.T.O.A.C and n-butanol was advantageously used to develop an ultrasound-assisted dispersive liquid-liquid microextraction (U.A-D.L.L.M.E) method combined with high-performance liquid chromatography-ultraviolet detection (H.P.L.C-U.V) for the determination of some strobilurin fungicides in apple samples. Several important parameters influencing extraction efficiency were investigated and optimised, including the type and volume of extractant in ultrasound stage, sonication time, the type and volume of D.E.S, sample solution pH and effect of salt addition. Under optimal experimental conditions, the method showed good linearity with correlation coefficients (R²) of 0.9985 - 0.9991 in the linear range of 4-1500 μg kg^-1, low limits of detection of 1.5-2 μg kg^-1 and acceptable extraction recoveries in the range of 76-92%. Enrichment factor was in the range of 95-115. The proposed method was successfully applied for the extraction and preconcentration of trace fungicides in apple samples, and the results demonstrated the potential of the synthesised D.E.S for the extraction and determination of contaminants in aqueous samples.

Novel hydrophobic deep eutectic solvent for vortex-assisted liquid phase microextraction of common acaricides in fruit juice followed by HPLC-UV determination

In the present research, several novel and natural hydrophobic deep eutectic solvents (DESs) were prepared using methyltrioctylammonium chloride (MTOAC) as the hydrogen bond acceptor (HBA) and different types of straight chain alcohols as hydrogen bond donors (HBDs). One of the DESs composed of MTOAC and n-butanol was advantageously used to develop a vortex-assisted liquid phase microextraction (VALPME) method combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) for the determination of common acaricides in fruit juice samples. Several important parameters influencing extraction efficiency were investigated and optimized, including the type and volume of DES, sample solution pH, effect of salt addition and, extraction and vortex time. Under optimal experimental conditions, the method showed good linearity with the correlation coefficients (R 2) of 0.9986-0.9991 in the linear range of 2-300 μg L-1, low limits of detection of 0.5-1 μg L-1 and acceptable extraction recoveries in the range of 85-93%. The proposed method was successfully applied for the extraction and preconcentration of trace acaricides in real fruit juice samples, and the results demonstrated the potential of the synthesized DESs for the extraction and determination of contaminants in aqueous samples.