Supramolecular Solvent Research Articles

Eco-friendly solvents in liquid-liquid microextraction techniques for biological and environmental analysis: a critical review.

In recent years, green solvents have emerged as promising alternatives in the field of analytical chemistry, replacing conventional organic solvents known for their toxicity, volatility, and flammability. The combination of these solvents with liquid-liquid microextraction techniques has facilitated the development of simpler, faster, more economical, and environment-friendly methodologies for the analysis of samples of varying complexity. This review discusses the fundamental physicochemical properties and advantages of using deep eutectic solvents, ionic liquids, switchable-hydrophilicity solvents, supramolecular solvents, and surfactants as extractants. Furthermore, analytical methods based on liquid-liquid microextraction techniques developed in the last 5years for the determination of organic compounds and metals in biological and environmental samples are presented and discussed, highlighting their applications and benefits to improve analytical performance and sustainability.

Preparation of a New Hexafluorobutanol-Farnesol Based Supramolecular Solvent and Its Application in Microextraction of Sudan Dyes From Beverage and Water Samples.

In this work, a new supramolecular solvent (SUPRAS) was prepared for the first time using hexafluorobutanol (HFB) and farnesol (FO). FO acts as an amphiphile and HFB as a coacervation inducer and density regulator. The method of dispersive liquid-liquid microextraction followed by high-performance liquid chromatography, supported by a vortex technique, was established using the prepared SUPRAS for the determination of Sudan dyes in aqueous samples. The extraction parameters, including FO content, HFB content, vortex time, salt addition, and solution pH, were thoroughly investigated and optimized. Under the optimized conditions, the linearity range is 10-750ng/mL for Sudan I, and 10-1000ng/mL for Sudan III and Sudan IV, respectively. The limits of detection for Sudan dyes were in the range of 0.8-3.1ng/mL. The inter- and intra-day relative standard deviations for Sudan dyes were in the range of 1.3%-4.1% and 0.2%-2.6%, respectively. Finally, the proposed method was applied to the determination of Sudan dyes in beverage and river water samples with recoveries ranging from 93.9% to 122.1%. Compared to conventional techniques for the extraction of Sudan dyes in real samples, the proposed method is simpler, faster, and more environmentally friendly.

A novel approach based on supramolecular solvents microextraction for quick detection of perfluoroalkyl acids and their precursors in aquatic food

Per-and polyfluoroalkyl substances (PFASs) have garnered significant attention owing to their prevalence and adverse effects on humans. The direct dietary intake of perfluoroalkyl acids (PFAAs) and PFAAs precursors (pre-PFAAs) biotransformation are considered major contributors to human exposure to PFASs. However, little information is available on analytical methods for the simultaneous detection of PFAAs and pre-PFAAs. In the present study, a single-step sample-treatment-based supramolecular solvents-dispersed liquid-liquid microextraction (SUPRASs-DLLME) technique was established for the analysis of 16 PFAAs and 7 pre-PFAAs in aquatic food. SUPRASs were synthesized using 1-heptanol (3 mL) and tetrahydrofuran (4 mL), which were self-assembled in water. The parameters for microextraction, such as extraction method and enrichment capacity, were optimized. Under the optimum conditions, the limit of detection (LOD) and limit of quantification (LOQ) were 0.03–0.15 ng·g−1 and 0.1–0.5 ng·g−1, respectively. Good linearities (R2 > 0.996) were obtained for all the target compounds, and the recoveries ranged 81.1–120 % with relative standard deviations (RSDs) lower than 20 %. This method was applied to the analysis of 16 PFAAs and 7 pre-PFAAs in aquatic food samples (crabs, prawns, and fish). This study provides a new idea for analyzing other pollutants in biological samples.

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.

Supramolecular Solvent Liquid Phase Microextraction of Voriconazole İn Pharmaceutical and Environmental Samples With High Performance Liquid Chromatography Detection

In this study, a new analytical method based on the supramolecular solvent liquid phase microextraction (Ss-LPME) and HPLC was developed for the analysis of voriconazole as an active drug in the class of antifungals with a wide spectrum of action at trace levels. Nano/micro sized supramolecular phase formed in 1-decanol, tetrahydrofuran and aqueous environment was used as extraction agent for separation and preconcentration of trace level of voriconazole. For the optimization of the Ss-LPME method, important analytical parameters such as the effect of sample solution pH, volume of 1-decanol, amount of THF, ultrasounic irridation time, centrifugation time and sample solution volume on the extraction efficiency were evaluated. Optimal conditions of the Ss-LPME; pH: 8, 1-decanol volume: 200 µL, THF volume: 300 µL, ultrasounic irridation time:10 min and centrifugation time: 8 min. For the developed Ss-LPME/HPLC procedure, the limit of detection (LOD), limit of quantification (LOQ) and enhancement factor (EF) were found 2.7 µg·L-1, 8.8 µg·L-1 and 36, respectively. The Ss-LPME/HPLC procedure was applied to waste water, lake water and drug samples. The fact that recovery values ranging from 100% to 108.5% were obtained for these real samples proved that this method can be used successfully in the matrix environments studied

Evaluation of a simultaneous approach to concentrate and preserve bioactive compounds with distinct polarities by employing supramolecular solvents (SUPRAS)

Supramolecular solvents (SUPRAS) have attracted attention as eco-friendly and highly effective solvents that can be tailored to solubilize compounds with distinct polarities. This study investigated the SUPRAS/equilibrium solution systems’ (SUPRAS-EqS) capacity to concentrate and preserve bioactive compounds through simultaneous solvent production and a liquid–liquid separation method. For this, β-carotene, quercetin, and curcumin were evaluated as molecular probes. SUPRAS-EqS systems were produced with octanoic acid (5 %, v/v), ethanol (20–––35 %, v/v), and acidified water (75–––60 %, v/v) and characterized concerning SUPRAS phase formation and their composition. Moreover, the SUPRAS phase’s ability to preserve these compounds during thermal exposure was evaluated at 313.15 K, 323.15 K, and 333.15 K and compared with an ethanolic medium. The outcomes demonstrated the formation of spherical supramolecular aggregates (10 to 20 μm), where the size of coacervates increased proportionally with the ethanol concentration. Concerning the separation efficiency provided by the SUPRAS phase, all compounds exhibited values superior to 83 %, and the systems produced with 22.5 % ethanol for quercetin and curcumin, and 27.5 % ethanol for β-carotene, presented the highest partition coefficient values. The SUPRAS phase promoted a more suitable environment to preserve the bioactive compounds than ethanol, and quercetin exhibited the highest half-life time values. Curcumin displayed the strongest activation energy in both the SUPRAS phase (48.88 kJ/mol) and the ethanol media (54.50 kJ/mol), indicating its high temperature dependence compared to the other compounds. These findings highlight the SUPRAS phase capacity to concentrate and stabilize bioactive compounds individually with different polarities.

Supramolecular solvent for the vortex-assisted dispersive liquid–liquid microextraction of aristolochic acids from Aristolochia debilis prior to HPLC-DAD

In this study, a new vortex-assisted dispersive liquid–liquid microextraction technique based on supramolecular solvent (SUPRAS) was proposed for the simultaneous extraction and preconcentration of aristolochic acids (AAs) in Aristolochia debilis followed by HPLC-DAD. A new type of SUPRAS, based on hexafluoroisopropanol (HFIP) and primary amine, with a higher density than water was prepared for the first time. HFIP acted as the coacervation agent and density modifier for the preparation of SUPRAS, and only a small amount of HFIP was required to form the SUPRAS. The influencing parameters such as the type and content of primary amine, the content of HFIP, vortex time, solution pH and ionic strength were thoroughly investigated and optimized. The prepared SUPRAS can effectively exclude macromolecules such as starch and be used to extract AAs from herbal medicines with high extraction efficiency. Under the optimized conditions, the method provided satisfactory linearity (1 ∼ 1000 ng mL−1 for AAb and 10 ∼ 1000 ng mL−1 for AAa with determination coefficients higher than 0.9981), low limits of detection (0.3 ∼ 3.1 ng mL−1) and limits of quantification (1.0 ∼ 9.5 ng mL−1). In addition, the intra-day and inter-day precision with relative standard deviations (RSDs%) below 6.8 % were obtained. Finally, the proposed method was applied to determine the AAs in Aristolochia debilis, the extraction recoveries were between 92.8 %∼100.6 % with RSDs% between 0.5 % and 7.2 %. Therefore, the developed method was an easy, efficient and reliable method for determining AAs in Aristolochia herbal materials.

A high-throughput sample preparation approach for the determination of nonsteroidal anti-inflammatory drugs in urine samples through membrane-based microextraction employing a green supramolecular solvent

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a class of drugs with antipyretic, analgesic, and anti-inflammatory effects widely used worldwide. This study aimed at developing an environmentally friendly and high-throughput sample preparation method for the determination of six NSAIDs in urine samples followed by high-performance liquid chromatography coupled to diode-array detection (HPLC-DAD). The experimental workflow consisted of hollow-fiber microporous membrane liquid-liquid extraction (HF-MMLLE) using a supramolecular solvent immobilized into the porous of polypropylene hollow membranes (1 cm length). These membranes were attached to a 96-well plate system to permit multiple extractions simultaneously. Under the optimized conditions, limits of detection (LODs) and limits of quantification (LOQs) ranged from 6.06 to 30.3 µg/L and from 20 to 100 µg/L, respectively. The linear ranges varied from 20 to 1000 µg/L for indomethacin and diclofenac, from 50 to 1000 µg/L for ketoprofen and ibuprofen, and from 100 to 1000 µg/L for naproxen and fenoprofen. The coefficients of determination (R²) ranged from 0.9735 to 0.9997. Intraday precision ranged from 6.13 to 20.11 %, interday precision varied from 2.87 to 20.72 %, and accuracy ranged from 92.49 to 126.89 %. Moreover, the recently proposed Sample Preparation Metric of Sustainability (SPMS) was employed to evaluate the greenness of the sample preparation technique resulting in a score of 8.0, which is highly satisfactory according to the concepts of green analytical chemistry.

Development and validation of a green analytical method for determining fourteen bisphenols in bee pollen by ultra-high-performance liquid chromatography-tandem mass spectrometry

A new analytical method was developed and validated to determine fourteen bisphenols (A, B, C, E, F, M, P, S, Z, AF, AP, BP, FL, PH) in bee pollen using ultra-high-performance liquid chromatography-tandem mass spectrometry. Two different sample treatments were proposed and evaluated: one based on the QuEChERS (quick, easy, cheap, effective, rugged & safe) approach and the other utilizing microextraction with a supramolecular solvent (SUPRAS). In both cases, average analyte recovery ranged between 71 % and 114 %, and the matrix effect was between −45 % and +5 %, although it was not significant when using the QuEChERS-based method (<±20 %). The environmental impact of both sample treatments was assessed using different analytical metrics, with both procedures classified as environmentally friendly, though slightly better results were obtained for SUPRAS. The method was fully validated, showing that the QuEChERS approach had better overall performance, particularly regarding sensitivity and matrix effect. Consequently, the QuEChERS methodology was applied to determine bisphenols in thirty bee pollen samples from different Spanish regions. Residues of three bisphenols (M, P, and S) were detected, although only bisphenol S was quantified in several samples at low concentration levels (<7 μg kg−1), which is below the established specific migration limit (SML; 50 μg kg−1). However, regarding human health, the estimated daily intake, target hazard quotient, and hazard index assessed were higher than acceptable limits, suggesting a potential risk for human consumers.

Primary alcohol-induced coacervation in alkyl polyglucoside micellar solution for supramolecular solvent-based microextraction and chromatographic determination of phthalates in baby food

This study reports for the first time the phenomenon of supramolecular solvent formation based on alkyl polyglucoside as an amphiphile and primary alcohol as a coacervation agent. The physical properties (density, kinematic viscosity, phase diagram for ternary system) of the supramolecular solvent were investigated, and a mechanism for its formation was proposed. A green and simple microextraction procedure for preconcentration and determination of phthalates in baby foods packaged in plastic packaging was developed as proof-of-concept example. The microextraction procedure assumed separation of analytes from solid phase sample in micellar solution of decyl glucoside and in situ formation of supramolecular solvent for analytes preconcentration after addition of n-heptanol. The determination of phthalates in obtained extracts was implemented by high-performance liquid chromatography with UV–Vis detection. The limits of detection, calculated from a blank test based on 3σ, were determined to be 10 μg kg−1 for dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, and di-n-octyl phthalate. The developed procedure did not require filtration of sample suspension, and assumed the use of green and biodegradable substances for the supramolecular solvent formation across a wide pH range.

Supramolecular solvents based on hydrophobic natural deep eutectic solvents and primary amines for preconcentration and determination of enrofloxacin in milk

In this work, coacervation in primary amines solutions with hydrophobic natural deep eutectic solvents based on terpenoids and carboxylic acids was demonstrated for the first time. A liquid-phase microextraction approach was developed based on supramolecular solvent formation with primary amine acting as amphiphile and hydrophobic deep eutectic solvent making up mixed vesicles and serving as coacervation agent. Such supramolecular solvents could be used to separate wide range of substances from different aqueous media, such as food products, biological liquids and wastewaters. It is important that both hydrophobic and ionic interactions with supramolecular aggregates take place ensuring synergetic effect and better extraction ability, which is significant in separating relatively polar analytes. Different primary amines and deep eutectic solvents were investigated for liquid-phase microextraction of proof-of-concept amphoteric analyte (enrofloxacin, widely used veterinary fluoroquinolone antibiotic) and its determination by high-performance liquid chromatography with fluorescence detection using Shimadzu LC-20 Prominence chromatograph and RF-20A fluorescence detector. It was found that the supramolecular solvent based on 1-nonylamine, formed after addition of a deep eutectic solvent based on menthol and hexanoic acid (molar ratio of 1:1), provided maximum extraction recovery (85 %) and maximum enrichment factor (34). To characterize the extraction system, the composition of the phases was investigated, and cryo-transmission electron microscopy images were obtained. Vesicular aggregates were observed in the supramolecular solvent. The extraction mechanism was proposed in terms of formation of mixed aggregates to capture the analyte. Limit of detection was found to be 7 μg kg−1, while linear range of 20–250 μg kg−1 was established. Relative standard deviation values were lower than 7 %. Relative bias did not exceed 12 %.

A simple and efficient supramolecular solvent based liquid phase microextraction method for the preconcentration of nickel from dandelion tea samples before FAAS quantification, and the practicality and greenness assessment of developed method

A sensitive, accurate and practical analytical method (supramolecular solvent based liquid phase microextraction – flame atomic absorption spectrometry (SUPRAS-LPME-FAAS) was developed for the determination of nickel in dandelion tea samples. All influential parameters of SUPRAS-LPME were optimized to attain low detection/quantification limits using a univariate optimization approach. Under the optimum SUPRAS-LPME-FAAS conditions, dynamic range, limit of detection (LOD) and limit of quantification (LOQ) were found to be 25.86–497.64 µg/kg, 8.20 µg/kg and 27.35 µg/kg, respectively. The detection power of FAAS system was augmented as 28-fold with the help of SUPRAS-LPME method. Recovery experiments were performed for the evaluation of the accuracy and the applicability of the SUPRAS-LPME-FAAS method and percent recovery results for the spiked dandelion tea samples were calculated between 86.0 and 131.8 % via matrix matching calibration strategy. Additionally, the practicality and greenness evaluations for the SUPRAS-LPME-FAAS method were carried out using BAGI and AGREEprep software, respectively.

Research progress on pretreatment technology for the analysis of amphetamine biological samples.

Sample pretreatment technology is crucial for drug analysis and detection, because the effect of sample pretreatment directly determinates the final analysis results. In recent years, with the continuous innovation of microextraction and other technologies like material preparation technologies and assistant technologies for extraction, the sample pretreatment techniques in the process of drug analysis have become more and more mature and diverse. This article takes amphetamine (AM) or methamphetamine as an example to review the recent development of pretreatment methods for AM-containing biological samples from the perspectives of extraction techniques, extraction media and auxiliary technologies. Extraction techniques are summarized with the categories of contact microextraction, separate microextraction and membrane-based microextraction for better guidance of application according to their features. Prevailing and innovative extraction media including carbon-based material, silicon-based material, metal organic framework, molecularly selective materials, supramolecular solvents and ionic liquids are reviewed. Auxiliary technologies like magnetic field, electric field, microwave, ultrasound and so on which can enhance extraction efficiency and accuracy are also reviewed. In the last, prospects of the future development of pretreatment technology for the analysis of AM biological samples are provided.

Hexafluoroisopropanol-based supramolecular solvent for liquid phase microextraction of pesticides in milk

Residues of pesticides in milk may pose a threat to human health. This study aimed to develop a liquid-phase microextraction (LPME) method using hexafluoroisopropanol (HFIP)-based supramolecular solvent (SUPRAS) for the simultaneous extraction and purification of four pesticides (boscalid, novaluron, cypermethrin and bifenthrin) in milk. Pesticides were extracted using SUPRAS prepared with nonanol and HFIP, and the extraction efficiency was analyzed. Results showed satisfactory recoveries ranging from 80.8%–111.0%, with relative standard deviations (RSDs) of <6.4%. Additionally, satisfactory linearities were observed, with correlation coefficients >0.9952. The limits of quantification (LOQs) were in the range of 1.8 μg·L−1–14.0 μg·L−1. The established method demonstrated high extraction efficiency with a short operation time (15 mins) and low solvent consumption (2.7 mL). The HFIP-based SUPRAS LPME method offers a convenient and efficient approach for the extraction of pesticides from milk, presenting a promising alternative to conventional techniques.

Green Liquid-Phase Microextraction Using Nonanoic Acid as a Novel Extractant for the Spectrophotometric Determination of Rhodamine B in Cosmetics

A new method for separating and concentrating Rhodamine B (RhB) in cosmetics has been developed using nonanoic acid liquid-phase microextraction (NA-LPmE) with spectrophotometric determination. Nonanoic acid is a novel and environmentally friendly extractant that was used as a single component in the isolation. In contrast, supramolecular solvents and deep eutectic solvents are often combined as a mixture. The method is simple, quick, accurate, and environmentally friendly. The appropriate parameters (the volume of NA, pH, sample volume, and matrix effects) were optimized and these conditions resulted in a suitable linear range (20.5–1000 µg L−1), low detection limit (6.2 µg L−1), and high pre-concentration factor (40). The NA-LPmE method successfully extracted and determined RhB in several cosmetics and employs a small volume of green solvent with spectrophotometric determination and rapid analysis. The combination of nonanoic acid and RhB was used for the first time.

Air-assisted solidified floating organic drop microextraction method based on green supramolecular solvent for arsenic and selenium qantification in water and food samples

A supramolecular solvent (SUPRAS) was prepared from undecanoic acid and tetrabutylammonium hydroxide and used as an extraction solvent. A fast microextraction approach based on air-assisted solidified floating organic drop (AA-SFODME) coupled to a hydride generation atomic absorption spectrometer (HG-AAS) for arsenic and selenium traces determination in water and food samples was developed. The air bubbles enhanced the extraction efficiency by reducing both the time and the required chemical amounts. The 2-((4-iodophenyl) diazenyl)-8-hydroxyquinoline (IPHQ) was used as a chelation reagent. The experimental factors that impact extraction efficiency were improved and optimized. The limits of detection (LODs) for arsenic and selenium were 0.09 and 0.07 µg L−1, respectively. Also, the preconcentration factors (PFs) and enhancement factors (EFs) were found to be 100 and 103 for both arsenic and selenium, respectively. The linearity of both two calibration curves ranged from 0.10 to 700 µg L−1, with linear regression coefficients (R2) of 0.9986 and 0.9978, respectively. Finally, the greenness score was determined using two tools: the analytical greenness calculator (AGREE) and the Blue Applicability Grade Index (BAGI). The high greenness scores from these tools can make this method even more environmentally friendly and practical.

Development of a supramolecular solvent–based extraction method for application to quantitative analyses of a wide range of organic contaminants in indoor dust

This study investigates the efficacy of supramolecular solvent (SUPRAS) in extracting a diverse spectrum of organic contaminants from indoor dust. Initially, seven distinct SUPRAS were assessed across nine categories of contaminants to identify the most effective one. A SUPRAS comprising Milli-Q water, tetrahydrofuran, and hexanol in a 70:20:10 ratio, respectively, demonstrated the best extraction performance and was employed for testing a wider array of organic contaminants. Furthermore, we applied the selected SUPRAS for the extraction of organic compounds from the NIST Standard Reference Material (SRM) 2585. In parallel, we performed the extraction of NIST SRM 2585 with conventional extraction methods using hexane:acetone (1:1) for non-polar contaminants and methanol (100%) extraction for polar contaminants. Analysis from two independent laboratories (in Norway and the Czech Republic) demonstrated the viability of SUPRAS for the simultaneous extraction of twelve groups of organic contaminants with a broad range of physico-chemical properties including plastic additives, pesticides, and combustion by-products. However, caution is advised when employing SUPRAS for highly polar contaminants like current-use pesticides or volatile substances like naphthalene.

Supramolecular Solvent-Based Liquid–Liquid Microextraction and Preconcentration of Rhodamine B, Methyl Violet, and Eriochrome Black T in Water, Cosmetics, and Food with Spectrophotometric Quantification

Dyes are complex organic compounds that are utilized in many industries. However, excessive exposure to dyes increases susceptibility to various diseases. Their concentrations are below the detection level of many available analytical techniques. Therefore, preconcentration methodology is highly needed prior to their quantification. Herein, a new supramolecular solvent decanol-tetrahydrofuran-based liquid-liquid microextraction method has been established for the first time for the determination of Rhodamine B (Rh B), methyl violet (MV), and Eriochrome black T (EBT) in commercial spices, cosmetics, and water before spectrophotometric quantification. 556, 590, and 530 nm were used for the measurement of Rhodamine B (Rh B), methyl violet (MV), and Eriochrome black T (EBT), respectively. The optimization experiments revealed the best performance at pH 7, 0.9 mL of decanol, 1.3 mL of tetrahydrofuran (THF), and 5 min of vortex time. Under optimized conditions, the limits of detection (LOD) (0.480–0.511 µg L−1), limits of quantification (LOQ) (1.455–1.549 µg L−1), preconcentration factor (PF) (15–20), enhancement factor (EF) (15–20), and relative standard deviation (RSD) (0.5–0.8%) were evaluated. The validation of the method was carried out by standard addition experiments for food, cosmetic, and environmental water samples. The recovery results from 95 ± 6 to 100 ± 4% demonstrate that the method can be successfully applied to practical analysis.

A high-throughput supramolecular solvent method for benzophenone quantification in juice packs via liquid chromatography-mass spectrometry

Benzophenones (BPs) are among the most frequently detected photoinitiators in liquid packaged food, mainly using liquid chromatography tandem mass spectrometry (LC-MS/MS). However, sample treatments in these methods are demanding in terms of resources and expenses, are little or not sustainable, and prevent high throughput sample processing. In this paper, supramolecular solvents with properties of restricted access materials (SUPRAS-RAM) were firstly used to make simpler, faster and more sustainable the sample treatment in the determination of BPs in juices. The SUPRAS-RAM formed instantaneously in the juice by the addition of hexanol (75 µL) and tetrahydrofuran (600 µL). The BPs were extracted after vortexing the mixture for 2 min. Macromolecules in the sample, including carbohydrates, fibers and proteins were not extracted in the SUPRAS-RAM by physical or chemical mechanisms, so the extract could be directly injected into the LC-MS/MS system. Detection limits were in the range of 0.013–0.414ng mL−1. Average recoveries of BPs in juices (orange, tomato, pineapple, apple) at three concentration levels (1, 5 and 20ng mL−1) were 70.4–118 %, with relative standard deviations in the interval 0.05–9 %. Matrix effects were all in the range of ±20 %. Unlikely most of the reported methods for BPs based on LC-MS/MS, external calibration gave reliable quantification. Three BPs were detected and/or quantified in the ten juice samples analysed; namely benzophenone, 2-hydroxy-4-methoxybenzophenone and 4-methylbenzophenone. The characteristics of the sample treatment here proposed (i.e. low solvent consumption, integration of BP extraction and sample clean-up and a simple and fast procedure, and the effective removal of interferences) render this method competitive for BPs quantification with respect to previously reported methods.

Nano temperature-switchable supramolecular solvent: Preparation, characterization and application in efficient extraction and enrichment of phytochemicals

In this study, a nano temperature-switchable supramolecular solvent (NTS-SUPRAS) system was designed, prepared and characterized for efficient extraction and enrichment of phytochemicals, the extraction mechanism was also investigated. The NTS-SUPRAS was synthesized by natural deep eutectic (NADES), 1,2-Propanediol and water, then the ternary phase diagrams were plotted according to their mass fractions. Dynamic light scattering (DLS), conductivity and FT-IR were used to characterize the solvent, and an exciting discovery was the nanoscale of NTS-SUPRAS. The particle size of its reverse micelles self- aggregated was positively correlated to the water content, which was increased from 3.8 nm to 77.9 nm as the water content increased from 5 % to 20 %. Temperature-switchable of NTS-SUPRAS was proved by the appearance of phase separation when regulate temperature from 25 °C to 10 °C. Then, six phytochemicals in Cajanus cajan(Linn.) leaves were efficiently extracted and enriched by vortex-assisted extraction. The extraction factors such as solid–liquid ratio, vortex time, NADES content and water content were optimized using the one-factor optimization method and response surface analysis to obtain the optimal extraction conditions. The results showed that the extraction efficiency of NTS-SUPRAS was 1.18–2.32 folds higher than that of traditional solvents for different polar substances, and the total extraction yield could be reached 21.13 mg/g. The phytochemicals were highly recovered by temperature-switching and macroporous adsorption resin with a recovery rate up to 98.6 %, and the reusability of NTS-SUPRAS could still keep at 90.43 % of the initial one after three cycles. Finally, the extraction mechanism of NTS-SUPRAS was investigated using density functional theory (DFT), founding that the hydrogen bonding between NTS-SUPRAS and the phytochemicals was attributed to the high extraction rate. This nano temperature-switchable supramolecular solvent has the advantages of green, low cost, simple preparation, high extraction rate, easy recycling and good reusability, which is suitable for industrialized application and production. In addition, the nanoscale and the temperature-switchable characteristics also provide new prospects for high-value utilization of phytochemicals.