Solidification of floating organic droplet in dispersive liquid-liquid microextraction as a green analytical tool

Salt assisted liquid-liquid extraction combined with dispersive liquid-liquid microextraction for the determination of 24 regulated polycyclic aromatic hydrocarbons in human serum

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants of great concern due to their carcinogenicity and mutagenicity. Their determination in human serum, particularly in at-risk populations, is necessary but difficult because they are distributed over a wide range of polarity and are present at trace level. A new method combining salting-out assisted liquid-liquid extraction (SALLE) and dispersive liquid-liquid microextraction with solidification of floating organic drop (DLLME-SFO) adapted to a reduced volume of sample (100 µl) was developed to determine 24 PAHs in human serum. Some key parameters of DLLME-SFO (volume of extraction solvent, ratio of extraction/dispersive solvent volumes, and salt addition) were first studied by applying it to spiked pure water. For its application to serum, a sample treatment step involving SALLE was optimized in terms of nature and content of salts and applied upstream of DLLME-SFO. It was applied to the extraction of 24 regulated PAHs from spiked serum followed by an analysis by liquid chromatography coupled with UV and fluorescence detection. The extraction recoveries ranged from 48.2 and 116.0 % (relative standard deviations: 2.0-14.6 %, n=5-9), leading to limits of quantification of PAHs in human serum from 0.04 to 1.03 µg/L using fluorescence detection and from 10 to 40 µg/L using UV detection. This final method combining SALLE and DLLME-SFO showed numerous advantages such as no evaporation step, high efficiency and low solvent-consumption and will be useful for monitoring PAHs in low volumes of serum.

Solvent-Focused Gas Chromatographic Determination of Thymol and Carvacrol Using Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction through Solidifying Floating Organic Droplets (USA-DLLME-SFO)

An ultrasound-assisted dispersive liquid-liquid microextraction by solidifying floating organic droplets, coupled to a form of temperature-programmed gas chromatography flame ionization detection, has been developed for the extraction and determination of thymol and carvacrol. This method utilizes undecanol as the extraction solvent, offering advantages such as facilitating phase transfer through solidification and enhancing solvent-focusing efficiency. The optimal gas chromatography conditions include a sample injection volume of 0.2 µL, a split ratio of 1:10, and a flow rate of 0.7 mL min-1. The extraction conditions entail an extraction solvent volume of 20 µL, a disperser solvent (acetone) volume of 500 µL, pH 7.0, 7.0% NaCl (3.5 M), a sample volume of 5.0 mL, an ultrasound duration of 10 min, and a centrifuge time of 7.5 min (800 rpm). These conditions enable the achievement of a high and reasonable linear range of 3.5 to 70. 0 μg mL-1 for both thymol and carvacrol. The detection limits are found to be 0.95 and 0.89 μg mL-1, respectively, for thymol and carvacrol. The obtained relative standard deviations, 2.7% for thymol and 2.6% for carvacrol, demonstrate acceptable precision for the purpose of quantitative analysis.

Microextraction techniques for occupational biological monitoring: Basic principles, current applications and future perspectives

The application of green microextraction techniques (METs) is constantly being developed in different areas including pharmaceutical, forensic, food and environmental analysis. However, they are less used in biological monitoring of workers in occupational settings. Developing valid extraction methods and analytical techniques for the determination of occupational indicators plays a critical role in the management of workers' exposure to chemicals in workplaces. Microextraction techniques have become increasingly important because they are inexpensive, robust and environmentally friendly. This study aimed to provide a comprehensive review and interpret the applications of METs and novel sorbents and liquids in biological monitoring. Future perspectives and occupational indicators that METs have not yet been developed for are also discussed.

Recent Advances in Sample Preparation and Chromatographic/Mass Spectrometric Techniques for Detecting Polycyclic Aromatic Hydrocarbons in Edible Oils: 2010 to Present

Polycyclic aromatic hydrocarbons are considered to be potentially genotoxic and carcinogenic to humans. For non-smoking populations, food is the main source of polycyclic aromatic hydrocarbons exposure. Due to their lipophilic nature, oils and fats rank among the food items with the highest polycyclic aromatic hydrocarbon content. Consequently, the detection of polycyclic aromatic hydrocarbons in edible oils is critical for the promotion of human health. This paper reviews sample pretreatment methods, such as liquid-phase-based extraction methods, adsorbent-based extraction methods, and the QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, combined with detection techniques like mass spectrometry and chromatography-based techniques for accurate quantification of polycyclic aromatic hydrocarbons in edible oils since 2010. An overview on the advances of the methods discussed herein, along with a commentary addition of current challenges and prospects, will guide researchers to focus on developing more effective detection methods and control measures to reduce the potential risks and hazards posed by polycyclic aromatic hydrocarbons.

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.

Recent Advances in Dispersive Liquid-Liquid Microextraction for Pharmaceutical Analysis

Sample clean-up and pre-concentration are critical components of pharmaceutical analysis. The dispersive liquid-liquid microextraction (DLLME) technique is widely recognized as the most effective approach for enhancing overall detection sensitivity. While various DLLME modes have been advanced in pharmaceutical analysis, there need to be more discussions on pre-concentration techniques specifically developed for this field. This review presents a comprehensive overview of the different DLLME modes used in pharmaceutical analysis from 2017 to May 2023. The review covers the principles of DLLME, the factors affecting microextraction, the selected applications of different DLLME modes, and their advantages and disadvantages. Additionally, it focuses on multi-extraction strategies employed for pharmaceutical analysis.

Analytical Methods for the Determination of Quercetin and Quercetin Glycosides in Pharmaceuticals and Biological Samples

Flavonoids are plant-derived compounds that have several health benefits, including antioxidative, anti-inflammatory, anti-mutagenic, and anti-carcinogenic effects. Quercetin is a flavonoid that is widely present in various fruits, vegetables, and drinks. Accurate determination of quercetin in different samples is of great importance for its potential health benefits. This review, is an overview of sample preparation and determination methods for quercetin in diverse matrices. Previous research on sample preparation and determination methods for quercetin are summarized, highlighting the advantages and disadvantages of each method and providing insights into recent developments in quercetin sample treatment. Various analytical techniques are discussed including spectroscopic, chromatographic, electrophoretic, and electrochemical methods for the determination of quercetin and its derivatives in different samples. UV-Vis (Ultraviolet-visible) spectrophotometry is simple and inexpensive but lacks selectivity. Chromatographic techniques (HPLC, GC) offer selectivity and sensitivity, while electrophoretic and electrochemical methods provide high resolution and low detection limits, respectively. The aim of this review is to comprehensively explore the determination methods for quercetin and quercetin glycosides in diverse matrices, with emphasis on pharmaceutical and biological samples. The review also provides a theoretical basis for method development and application for the analysis of quercetin and quercetin glycosides in real samples.

Assessment of endocrine disruptor pollutants and their metabolites in environmental water samples using a sustainable natural deep eutectic solvent-based analytical methodology

In this work, an evaluation of the occurrence of fifteen phthalates, four metabolites and one adipate in different groundwater, seawater and wastewater samples has been carried out due to their relevance on human health as they act as endocrine disruptors. For this purpose, a sustainable, fast and easy-handling vortex-assisted liquid-liquid microextraction method using a natural hydrophobic deep eutectic solvent based on menthol and carvacrol as extraction agent, combined with ultra-high performance liquid chromatography-mass spectrometry technique, has been developed and applied for the first time. An optimization was performed to evaluate four important factors affecting the extraction performance, and an analytical validation was carried out in terms of matrix effect, linearity, extraction efficiency, and sensitivity. Recovery values were obtained in the range 72-119% for all analytes (except for monoethyl phthalate: 61.1-72.3%) with relative standard deviation values lower than 17%. Limits of quantification were found between 0.91 and 8.09 μg L-1. As a result of the assessment of 31 different environmental water samples, monoethyl phthalate, diethyl phthalate, dibutyl phthalate and bis (2-ethylhexyl) phthalate were detected and quantified at different concentrations in the range 2.59-21.17 μg L-1 in 6 samples, and diallyl phthalate, butyl benzyl phthalate, dipentyl phthalate, dicyclohexyl phthalate, dihexyl phthalate and bis (2-ethylhexyl) adipate were detected in 20 more, showing the exposition of the population to these hazardous substances.

Improved liquid-liquid extraction followed by HPLC-UV for accurate and eco-friendly determination of tetramethylpyrazine in vinegar products

Tetramethylpyrazine (TMP) is an important bioactive compound in vinegars, contributing to their health-enhancing attributes. It serves as a crucial benchmark for the assessment of vinegar quality. Unfortunately, inaccuracies have arisen due to incomplete extraction techniques and the use of an inappropriate standard substance. These challenges have significantly curtailed comprehensive exploration into the underlying TMP formation mechanisms, impeding advancements within prevailing benchmarks and methodologies governing vinegar products. To address these challenges, several critical parameters, encompassing pH, solvent type, centrifugal force, extraction times and reference materials were investigated and optimized. The TMP content was determined by adjusting the pH to 9 using a sodium hydroxide solution, followed by extraction with ethyl acetate and subsequent re-extraction of the ethyl acetate layer with 0.2 mol/L HCl. A high-performance liquid chromatography method with an ultraviolet detector (UV) was developed and validated. This method demonstrated superior sensitivity compared to existing methods, with a limit of detection (LOD) of 0.0237 μg/g, limit of quantification (LOQ) of 0.0829 μg/g, method limit of detection (MLOD) of 0.10 μg/g and method limit of quantitation (MLOQ) of 0.25 μg/g. The modified method exhibited excellent linearity for TMP in the range of 0.1-118.4 μg/mL, with a good correlation coefficient (R2 > 0.999). The recovery rate of TMP in vinegar products ranged from 82.4 to 96.2%. Consequently, the proposed method exhibits substantial promise for systematic inquiry into TMP formation mechanisms and for ensuring consistent quality control during the production of premium-grade vinegars.

Analytical Methodologies for the Estimation of Oxazolidinone Antibiotics as Key Members of anti-MRSA Arsenal: A Decade in Review

Gram-positive bacterial infections are among the most serious diseases related with high mortality rates and huge healthcare costs especially with the rise of antibiotic-resistant strains that limits treatment options. Thus, development of new antibiotics combating these multi-drug resistant bacteria is crucial. Oxazolidinone antibiotics are the only totally synthetic group of antibiotics that showed activity against multi-drug resistant Gram positive bacteria including MRSA because of their unique mechanism of action in targeting protein synthesis. This group include approved marketed members (tedizolid, linezolid and contezolid) or those under development (delpazlolid, radezolid and sutezolid). Due to the significant impact of this class, larger number of analytical methods were required to meet the needs of both clinical and industrial studies. Analyzing these drugs either alone or with other antimicrobial agents commonly used in ICU, in the presence of pharmaceutical or endogenous biological interferences, or in the presence of matrix impurities as metabolites and degradation products poses a big analytical challenge. This review highlights current analytical approaches published in the last decade (2012-2022) that dealt with the determination of these drugs in different matrices and discusses their advantages and disadvantages. Various techniques have been described for their determination including chromatographic, spectroscopic, capillary electrophoretic and electroanalytical methods. The review comprises six sections (one for each drug) with their related tables that depict critical figures of merit and some experimental conditions for the reviewed methods. Furthermore, future perspectives about the analytical methodologies that can be developed in the near future for determination of these drugs are suggested.

Microfluidic formation of surface nanodroplets using green deep eutectic solvents for liquid-liquid nanoextraction and controlled precipitation

HYPOTHESIS

Surface nanodroplets have recently been employed for in situ chemical analysis leveraging their low volume, e.g. O(10^-15 L), that enables rapid analyte extraction and pre-concentration. So far, most surface nanodroplets have been formed using single organic solvents such as 1-octanol, toluene, among others. Designing multicomponent surface nanodroplet with controllable composition is highly desirable for extending their application as extractant.

EXPERIMENT

Here, we formed surface nanodroplets using green deep eutectic solvent (gDES) composed of thymol and decanoic acid, both of which are naturally occurring chemicals. The influence of parameters such as flowrate and the composition of deep eutectic solvent on the surface nanodroplet formation were studied. As proof-of-concept, the gDES surface nanodroplets were further used to extract and detect trace amounts of fluorescent rhodamine 6G dye and copper ions from water.

FINDINGS

The formation of gDES surface nanodroplets follows the theoretical model which states that the final droplet volume (V_f) scales with the Peclét number (Pe) of the flow during formation by the solvent exchange process, that is V_f ∼ Pe^3/4, and the nanodroplets demonstrate excellent ability as extractant for rhodamine 6G and copper ions from water. Surprisingly, the confined volume of gDES surface nanodroplets enables fast and controlled formation of Cu (II)-decanoate crystal.

An environment-friendly approach using deep eutectic solvent combined with liquid-liquid microextraction based on solidification of floating organic droplets for simultaneous determination of preservatives in beverages

With the increase in environmental protection awareness, the development of strategies to reduce the use of organic solvent used during the extraction process has attracted wide attention. A simple and green ultrasound-assisted deep eutectic solvent extraction combined with liquid-liquid microextraction based on solidification of floating organic droplets method was developed and validated for the simultaneous determination of five preservatives (methyl paraben, ethyl paraben, propyl paraben, isopropyl paraben, isobutyl paraben) in beverages. Extraction conditions including the volume of DES, value of pH, and concentration of salt were statistically optimized through response surface methodology using a Box-Behnken design. Complex Green Analytical Procedure Index (ComplexGAPI) was successfully used to estimate the greenness of the developed method and compare with the previous methods. As a result, the established method was linear, precise, and accurate over the range of 0.5-20 μg mL^-1. Limits of detection and limits of quantification were in the range of 0.15-0.20 μg mL^-1 and 0.40-0.45 μg mL^-1, respectively. The recoveries of all five preservatives ranged from 85.96% to 110.25%, with relative standard deviation less than 6.88% (intra-day) and 4.93% (inter-day). The greenness of the present method is significantly better compared with the previous reported methods. Additionally, the proposed method was successfully applied to analysis of preservatives in beverages and is a potentially promising technique for drink matrices.

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.

Nanoextraction based on surface nanodroplets for chemical preconcentration and determination

Liquid-liquid extraction based on surface nanodroplets, namely nanoextraction, can continuously extract and enrich target analytes from the flow of a sample solution. This sample preconcentration technique is easy to operate in a continuous flow system with a low consumption of organic solvent and a high enrichment factor. In this review, the evolution from single drop microextraction to advanced nanoextraction will be briefly introduced. Moreover, the formation principle and key features of surface nanodroplets will be summarized. Further, the major findings of nanoextraction combined with in-droplet chemistry toward sensitive and quantitative detection will be discussed. Finally, we will give our perspectives for the future trend of nanoextraction.

Modified DLLME-GC-TQMS determination of pesticide residues in Gomti River, Lucknow, India: ecological risk assessment and multivariate statistical approach

This research article aims to establish an easy and well-defined analytical method for detection and quantification of multiclass pesticides in Gomti river water samples because the increased agricultural activities, industrialization, and urbanization had increased the presence of pesticides in the ecosystem which causes the depletion of water quality making it a global concern. The analytical method, vortex-assisted ultrasonication-based dispersive liquid-liquid microextraction-solidification of floating organic droplets (VAUS-DLLME-SFO) was optimized using one parameter at a time approach which gave the recovery between 69.45 and 114.15%, limit of detection (LOD), and limit of quantification (LOQ) 0.0011-0.0111 µg/L and 0.0033-0.0368 µg/L, respectively, and RSD in the range of 0.75-1.29 which shows sensitivity and accuracy better than earlier reported methods. The data obtained were subjected to measurement uncertainty, risk assessment, and multivariate statistical analysis to establish the robustness of the developed analytical method. The measurement uncertainty found was concluded to be in the acceptable range for analytical results. Furthermore, the real samples were analyzed and the associated value of the risk quotient was found to be less than 1, except for aquatic invertebrates, establishing the fact that the current concentration of pesticides has no such negative threat to flora and fauna. The possible source of pesticides in the Gomti river system was established by multivariate analysis. It was thus concluded that anthropogenic activity is responsible for the variable concentration of pesticides found in the sample.

Response surface optimization of a vortex-assisted dispersive liquid-liquid microextraction method for highly sensitive determination of repaglinide in environmental water by HPLC/UV

A vortex-assisted dispersive liquid–liquid microextraction (DLLME) method, mated to chemometrics and combined with HPLC/UV detection was optimized and validated for enrichment and determination of repaglinide in environmental samples using nateglinide as an internal standard (IS). A phosphate buffer (10 mM, pH 2.5): acetonitrile (45:55, v/v) was used as a mobile phase with a flow rate of 1 mL/min in an isocratic elution mode. Chemometrics-assisted optimization was performed using a quadratic integrated d-optimal design. The developed model assessed the statistical significance of the independent variables and their interactions to attain the optimum conditions revealing that extractant type, extractant volume and pH are the most influential factors. Optimization of the extraction procedures was performed with the aid of Design Expert 8® software, which suggested 58 different experiments. The optimal conditions were 30 µL of 1-octanol as extractant, 100 µL of acetonitrile as a disperser at pH 8. Under the optimized conditions, the method showed linearity over the range of 1–100 ng/mL with a limit of detection of 0.4 ng/mL. The accuracy, the intra- and inter-day precision were assessed, the %recoveries were found to be between 98.48 and 100.81% with %RSD lower than 1.3. Using chemometrics in method optimization helped achieve the maximum possible enrichment with the least effort, time, and reagents while considering all possible interactions between variables.

Rapid analysis of triazine herbicides in fruit juices using evaporation-assisted dispersive liquid-liquid microextraction with solidification of floating organic droplets and HPLC-DAD

A rapid and convenient analytical procedure (evaporation-assisted dispersive liquid-liquid microextraction with solidification of floating organic droplets) is advanced for determining the concentrations of triazine herbicide residues (e.g. simazine and atrazine) in fruit juices via HPLC-DAD. The technique involves adding 1-dodecanol (low density) and dichloromethane (high density) to the test solution to act as the extraction and volatile solvents, respectively. Calcium oxide is added to generate heat to accelerate the evaporation of dichloromethane, whereupon the 1-dodecanol quickly disperses into small droplets to complete the microextraction process. Thus, there is no need to use a dispersive solvent and heating equipment is also not required. The floating 1-dodecanol is subsequently frozen using an ice bath to facilitate its separation from the sample. Under optimal conditions (250 μL of 1-dodecanol (extraction solvent), 150 μL of CH₂Cl₂ (volatile solvent), 1250 mg of CaO, and an extraction time of 60 s) the detection procedure is linear over the range 0.05-5 μg mL^-1 (with R > 0.99). The limits of detection (LOD) and quantification (LOQ) were determined to be 0.0022-0.0034 μg mL^-1 and 0.0073-0.0113 μg mL^-1, respectively. The recovery of simazine and atrazine in three fruit juices ranged between 78.5% and 96.4% with a relative standard deviation <8.2%. Therefore, the proposed approach can be effectively adopted to analyze the triazine herbicide content in fruit juices. The method has been proved to be simple, reliable, and remarkably efficient.

A Gadolinium-Based Magnetic Ionic Liquid for Supramolecular Dispersive Liquid-Liquid Microextraction Followed by HPLC/UV for Determination of Favipiravir in Human Plasma

Favipiravir is a potential antiviral medication that has been recently licensed for COVID-19 treatment. In this work, a gadolinium based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid-liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50mg of the Gd-MIL and 150μL of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to FDA bioanalytical method validation guidelines. The coefficient of determination was found to be 0.9999, for a linear concentration range of 25 to 1.0 × 10⁵ ng/mL. The percent recovery (accuracy) varied from 99.83 to 104.2 %, with % RSD values (precision) ranging from 4.07 to 11.84 %. Total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was found simple, selective and sensitive for determination of favipiravir in real human plasma.

Current development of bioanalytical sample preparation techniques in pharmaceuticals

Sample preparation is considered as the bottleneck step in bioanalysis because each biological matrix has its own unique challenges and complexity. Competent sample preparation to extract the desired analytes and remove redundant components is a crucial step in each bioanalytical approach. The matrix effect is a key hurdle in bioanalytical sample preparation, which has gained extensive consideration. Novel sample preparation techniques have advantages over classical techniques in terms of accuracy, automation, ease of sample preparation, storage, and shipment and have become increasingly popular over the past decade. Our objective is to provide a broad outline of current developments in various bioanalytical sample preparation techniques in chromatographic and spectroscopic examinations. In addition, how these techniques have gained considerable attention over the past decade in bioanalytical research is mentioned with preferred examples. Modern trends in bioanalytical sample preparation techniques, including sorbent-based microextraction techniques, are primarily emphasized.

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Bioanalytical sampling techniques are described with suitable applications in pharmaceuticals.

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The pros and cons of each bioanalytical sampling techniques are described.

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Relevant biological matrices are outlined.

Artificial networks for spectral resolution of antibiotic residues in bovine milk; solidification of floating organic droplet in dispersive liquid-liquid microextraction for sample treatment

The intensive use of antibiotics in livestock practice has a negative impact on human health and increases the antibiotic resistance. In this study feasible data interpretation algorithm along with efficient extraction protocol were combined for selective analysis of three antibiotics in milk samples. Trimethoprim, sulphamethoxazole and oxytetracycline are widely used antibiotics in veterinary pharmaceuticals. The studied antibiotics were efficiently extracted from milk samples with solidification of floating organic droplet in dispersive liquid-liquid microextraction. This extraction protocol was optimized not only to maximize extraction recoveries but also to approach the lower residue limits specified by European Union. Artificial neural networks succeeded in resolving spectral overlap between the studied drugs. The network architecture was optimized and validated for accurate and precise analysis. The proposed method outweighs the reported chromatographic methods for being simple and inexpensive and compared favorable to official methods.

Determination of favipiravir in human plasma using homogeneous liquid-liquid microextraction followed by HPLC/UV

Background: Favipiravir is an antiviral drug that was recently approved for the management of COVID-19 infection. Aim: This work aimed to develop a new method, using sugaring-out induced homogeneous liquid-liquid microextraction followed by HPLC/UV for the determination of favipiravir in human plasma. Materials & methods: The optimum extraction conditions were attained using 500 μl of tetrahydrofuran as an extractant and 1400 mg of fructose as a phase-separating agent. Results: The developed method was validated according to the US FDA bioanalytical guidelines and was found linear in the range of 25-80,000 ng/ml with a correlation coefficient of 0.999. Conclusion: These results showed that the developed method was simple, easy, valid and adequately sensitive for determination of favipiravir in plasma for bioequivalence studies.

An enhanced dispersive liquid–liquid microextraction method based on solidification of floating organic drops for the determination of pyrethroid pesticides in tea infusions

A novel enhanced dispersive liquid–liquid microextraction method based on solidified floating organic solvents containing [P4,4,4,12][PF6] and a hydrophobic solvent mixture for the determination of four pyrethroid insecticides in tea infusions.

QuEChERS sample preparation integrated to dispersive liquid-liquid microextraction based on solidified floating organic droplet for spectrometric determination of sudan dyes: A synergistic approach

In this project, a synergistic approach has been proposed where a quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation technique was developed for the extraction of sudan III and sudan IV dyes in different spices prior to its dispersive liquid-liquid microextraction based on solidified floating organic droplet (DLLME-SFO). Initially, the sample was extracted by QuEChERS method and then preconcentrated through DLLME-SFO followed by spectrophotometric detection. All the experimental parameters i.e., volume of extraction solvent, pH, acetonitrile to water ratio, temperature, centrifugation rate and time, and sample volume were optimized. Limit of detection (LOD) calculated for sudan III and sudan IV were 0.42 and 0.35 mg/L, respectively. Excellent recoveries were obtained in the range of 98.29-99.88%. After validation through standard addition methodology, the developed QuEChERS@DLLME-SFO method was successfully applied to determine sudan (III-IV) dyes in real spices samples. Integration of QuEChERS and DLLME-SFO was found to be a suitable substitute to eliminate the usage of costly primary secondary amines and other sorbents. The synergistic approach of QuEChERS and DLLME-SFO with the aid of UV/visible spectrophotometry makes it prompt, cost effective technique with excellent analytical figures of merit.

Deep Eutectic Solvents as Promising Green Solvents in Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Droplet: Recent Applications, Challenges and Future Perspectives

Deep eutectic solvents (DESs) have recently attracted attention as a promising green alternative to conventional hazardous solvents by virtue of their simple preparation, low cost, and biodegradability. Even though the application of DESs in analytical chemistry is still in its early stages, the number of publications on this topic is growing. Analytical procedures applying dispersive liquid-liquid microextraction based on the solidification of floating organic droplets (DLLME-SFOD) are among the more appealing approaches where DESs have been found to be applicable. Herein, we provide a summary of the articles that are concerned with the application of DESs in the DLLME-SFOD of target analytes from diverse samples to provide up-to-date knowledge in this area. In addition, the major variables influencing enrichment efficiency and the microextraction mechanism are fully investigated and explained. Finally, the challenges and future perspectives of applying DESs in DLLME-SFOD are thoroughly discussed and are critically analyzed.

Vortex-assisted natural deep eutectic solvent dispersive liquid-liquid microextraction based on the solidification of a floating organic drop for the determination of benzoic acid and sorbic acid in condiments

A simple, inexpensive, reliable and environmentally friendly method based on vortex-assisted dispersive liquid-liquid microextraction combined with solidification of a floating organic drop (VA-DLLME-SFO) followed by high performance liquid chromatography with a diode array detector (HPLC-DAD) was developed to determine benzoic acid (BA) and sorbic acid (SA) in ketchup and powder bags of instant noodles. Hydrophobic natural deep eutectic solvents (NADESs), as the microextraction solvent, were prepared with ternary components. Acetic acid can reduce the viscosity of hydrophobic NADESs and vortex can promote the dispersion of NADESs in aqueous solvents. In the DLLME process, several key parameters were optimized, including the type and volume of hydrophobic NADES, pH value, vortex time and salt content. Meanwhile, these parameters were assessed using response surface methodology based on the Box-Behnken design (BBD). Under optimal conditions, the developed method showed good linearity in the selected range (r², 0.9997). The limits of detection were 0.2 μg mL^-1 and 0.07 μg mL^-1 for BA and SA, respectively. Recoveries were in the range of 82.21% to 102.70% and the relative standard deviations (intra-day and inter-day precisions) were less than 5.66%. The proposed method was successful in analyzing BA and SA in ketchup and powder bags of instant noodles.

Homogeneous liquid-liquid extraction as an alternative sample preparation technique for biomedical analysis

Liquid-liquid extraction is a widely used technique of sample preparation in biomedical analysis. In spite of the high pre-concentration capacities of liquid-liquid extraction, it suffers from a number of limitations including time and effort consumption, large organic solvent utilization, and poor performance in highly polar analytes. Homogeneous liquid-liquid extraction is an alternative sample preparation technique that overcomes some drawbacks of conventional liquid-liquid extraction, and allows employing greener organic solvents in sample treatment. In homogeneous liquid-liquid extraction, a homogeneous phase is formed between the aqueous sample and the water-miscible extractant, followed by chemically or physically induced phase separation. To form the homogeneous phase, aqueous samples are mixed with water-miscible organic solvents, water-immiscible solvents/cosolvents, surfactants, or smart polymers. Then, phase separation is induced chemically (adding salt, sugar, or buffer) or physically (changing temperature or pH). This mode is rapid, sustainable, and cost-effective in comparison with other sample preparation techniques. Moreover, homogeneous liquid-liquid extraction is more suitable for the extraction of delicate macromolecules such as enzymes, hormones, and proteins and it is more compatible with liquid chromatography with tandem mass spectrometry, which is a vital technique in metabolomics and proteomics. In this review, the principle, types, applications, automation, and technical aspects of homogeneous liquid-liquid extraction are discussed.

A natural deep eutectic solvent as a novel dispersive solvent in dispersive liquid-liquid microextraction based on solidification of floating organic droplet for the determination of pesticide residues

Current trends in analytical chemistry encourage the use of innocuous solvents to develop modern methods aligned with green chemistry. In this sense, natural deep eutectic solvents (NADESs) have emerged as a novel generation of green solvents which can be employed in sample treatments as an alternative to the toxic organic solvents commonly used so far. In this work, a new extraction method employs dispersive liquid-liquid microextraction based on a solid floating organic droplet (DLLME-SFO), by using a mixture composed of a less dense than water extraction solvent, 1-dodecanol, and a novel dispersive solvent, NADES. The methodology was proposed to extract and preconcentrate some pesticide residues (fipronil, fipronil-sulfide, fipronil-sulfone, and boscalid) from environmental water and white wine samples before analysis by liquid-chromatography coupled to ultraviolet detection (HPLC-UV). Limits of quantification (LOQs) lower than 4.5 μg L^-1, recoveries above 80%, and precision, expressed as RSD, below 15% were achieved in both samples showing that the proposed method is a powerful, efficient, and green alternative for the determination of these compounds and, therefore, demonstrating a new application for NADES in sample preparation. In addition, the DLLME-SFOD-HPLC-UV method was evaluated and compared with other reported approaches using the Analytical GREEnness metric approach, which highlighted the greenness of the proposed method.

Solidified floating organic droplet microextraction coupled with HPLC for rapid determination of trans, trans muconic acid in benzene biomonitoring

Benzene is one of the carcinogenic compounds in the work environments. Exposure assessment of benzene through biological monitoring is an acceptable way to accurately measure the real exposure in order to conducting the health risk assessment, but it is always complicated, laborious, time consuming and costly process. A new sensitive, simple, fast and environmental friendly method was developed for the determination of urinary metabolite of benzene, trans trans muconic acid (t,t-MA) by dispersive liquid-liquid micro extraction based on solidification of floating organic droplet coupled with high-performance liquid chromatography with ultra violet detector. Central composite design methodology was utilized to evaluate the effective factors on the extraction output of the target metabolite. The calibration curve was plotted in the concentration ranges of 0.02-5 µg mL^-1. The precision and accuracy of the method were assayed via the relative standard deviation (RSD%) and relative recovery (RR%) using spiked samples with three replications. The RR% and RSD% of the optimized method were 86.9-91.3% and 4.3-6.3% respectively. The limit of detection (LOD) of the method was 0.006 µg mL^-1. The level of t,t-MA in real samples was ranged from 0.54 to 1.64 mg/g creatinine. We demonstrated that t,t-MA can be extracted and determined by an inexpensive, simple and fast method.

Insights into the Use of Phytoremediation Processes for the Removal of Organic Micropollutants from Water and Wastewater; A Review

Greater awareness of micropollutants present in water and wastewater motivates the search for effective methods of their neutralization. Although their concentration in waters is measured in micro- and nanograms per liter, even at those levels, they may cause serious health consequences for different organisms, including harmful effects on the functioning of the endocrine system of vertebrates. Traditional methods of wastewater treatment, especially biological methods used in municipal wastewater treatment plants, are not sufficiently effective in removing these compounds, which results in their presence in natural waters. The growing interest in phytoremediation using constructed wetlands as a method of wastewater treatment or polishing indicates a need for the evaluation of this process in the context of micropollutant removal. Therefore, the present work presents a systematic review of the effectiveness in the removal of micropollutants from polluted waters by processes based on plant used. The article also analyzes issues related to the impact of micropollutants on the physiological processes of plants as well as changes in general indicators of pollution caused by contact of wastewater with plants. Additionally, it is also the first review of the literature that focuses strictly on the removal of micropollutants through the use of constructed wetlands.

Sugaring-out induced homogeneous liquid-liquid microextraction as an alternative mode for biological sample preparation: A comparative study

Miniaturization of liquid-liquid extraction is a growing field of sample preparation to reduce solvent consumption, protect the environment, and preserve operators' health. In this work, four different modes of liquid-liquid microextraction have been compared including dispersive liquid-liquid microextraction, binary and ternary salting-out, and sugaring-out induced liquid-liquid microextraction. The extraction efficiency was evaluated by the enrichment factors of 14 different drugs from three pharmacological classes. Compared with the other modes, sugaring-out induced liquid-liquid microextraction was found to be the most efficient and, thus, it was applied for sample preparation of the antivirals in human plasma. Method optimization was performed using response surface methodology for the sugar type and amount (in mg), the sample pH, the equilibration time (in min), and the extractant volume (in µL). The method was then validated and found linear in the concentration range of 0.10-10 µg/mL for daclatasvir, 0.05-10 µg/mL for velpatasvir, and 0.20-10 µg/mL for ledipasvir, with correlation coefficients in the range 0.996-0.999. These results shows that sugaring-out induced liquid-liquid microextraction could be a more efficient microextraction mode for preparation of biological samples. Compared with other types of microextraction, sugaring-out induced liquid-liquid microextraction is greener, simpler, and cost-effective, with less tendency to affect the sample pH.

Recent advances in the extraction of triazine herbicides from water samples

Pesticides are excessively used in agriculture to improve the quality of crops by eliminating the negative effects of pests. Among the different groups of pesticides, triazine pesticides are a group of compounds that contain a substituted C₃ H₃ N₃ heterocyclic ring, and they are widely used. Triazine pesticides can be dangerous for humans as well as for the aquatic environment because of their high toxicity and endocrine disrupting effect. However, the concentration of these chemical compounds in water samples is low. Moreover, other compounds that may exist in the water samples can interfere with the determination of triazine pesticides. As a result, it is important to develop sample preparation methods that provide preconcentration of the target analyte and sufficient clean-up of the samples. Recently, a wide variety of novel microextraction and miniaturized extraction techniques (e.g., solid-phase microextraction and liquid-phase microextraction, stir bar sorptive extraction, fabric phase sorptive extraction, dispersive solid-phase extraction, and magnetic solid-phase extraction) have been developed. In this review, we aim to discuss the recent advances regarding the extraction of triazine pesticides from environmental water samples. Emphasis will be given to novel sample preparation methods and novel sorbents developed for sorbent-based extraction techniques.

Vortex-Assisted Dispersive Liquid-Liquid Microextraction Coupled with Deproteinization for Determination of Nateglinide in Human Plasma Using HPLC/UV

A validated method for preconcentration and determination of nateglinide in plasma was developed using vortex-assisted dispersive liquid-liquid microextraction. Different variables that affect extraction efficiency were studied and optimized, including type and volume of extractant, type and volume of disperser, pH of diluent, salt addition effect, centrifugation and vortex time. Nateglinide was extracted using 30 μL of 1-octanol as an extractant and 200 μL of methanol as a disperser. The enrichment factor reached 330 under the optimum conditions. High-performance liquid chromatography/ultraviolet was used for detection using phosphate buffer (pH 2.5, 10 mM): acetonitrile (45:55, v/v) as a mobile phase at a flow rate of 1 mL/min. The method was linear over the range of 50-20,000 ng/mL with a limit of detection of 15 ng/mL (signal-to-noise ratio = 3). Intra- and inter-day precision had %relative standard deviation <6% (n = 3) and the %recoveries were found to be between 102.5 and 105.9%. The proposed method is simple, sensitive, eco-friendly, cost-effective and powerful for microextraction of nateglinide from human plasma samples.

Extraction of phthalic acid esters from soft drinks and infusions by dispersive liquid-liquid microextraction based on the solidification of the floating organic drop using a menthol-based natural deep eutectic solvent

In this work, a natural deep eutectic solvent (NADES) consisting of L-menthol and acetic acid in a 1:1 molar ratio has been applied as extraction solvent for the dispersive liquid-liquid microextraction based on the solidification of the floating organic drop (DLLME-SFO) of a group of nine phthalic acid esters (dipropyl phthalate, DPP; butyl benzyl phthalate, BBP; dibutyl phthalate, DBP; dicyclohexyl phthalate, DCHP; diisopentyl phthalate, DIPP; di-n-pentyl phthalate, DNPP; di(2-ethylhexyl) phthalate, DEHP; diisononyl phthalate, DINP; and diisodecyl phthalate, DIDP) from three common infusions (camomile, pennyroyal mint, and linden teas) and three soft drinks (green tea, tonic, and lime and lemon drink), using dihexyl phthalate (DHP) and di-n-octyl phthalate (DNOP) as internal standards. After the DLLME-SFO procedure, analyses were carried out by high-performance liquid chromatography with UV detection. Method calibration showed good linearity for all the analytes and matrices, with determination coefficients (R²) higher than 0.9910. Relative recovery values were between 71 and 125 %, with relative standard deviation values in the range 1-22 % for the six types of samples, while the limits of quantification of the method were in the range 4.3-51.1 µg/L for infusions and in the range 3.5-33.3 µg/L for soft drinks. Several samples purchased in different local supermarkets were analysed, finding DPP, DBP, DIPP, DEHP and DINP, although only DPP, DBP and DEHP could be quantified in some of them.

[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.

Dispersive liquid-liquid microextraction based on a new hydrophobic deep eutectic solvent for the determination of phenolic compounds in environmental water samples

Dispersive liquid-liquid microextraction has garnered increasing attention in sample preparation due to its rapid and efficient extraction process. In this study, a new terpineol-based hydrophobic deep eutectic solvent was firstly synthesized by mixing α-terpineol with 1-octanoic acid, and then applied to analysis of phenols from water samples by dispersive liquid-liquid microextraction combined with high-performance liquid chromatography and diode array detection. Infrared spectroscopy indicated that hydrogen bonding was responsible for the formation of deep eutectic solvent between α-terpineol and 1-octanoic acid. After optimization of several parameters, such as the type and volume of deep eutectic solvent and the disperser, pH and ionic strength of sample solution, the developed method exhibited excellent extraction performance to the phenols with the enrichment factors from 27 to 32. Good linearity was acquired ranging from 5 to 5000 μg/L, and detection of limits of the proposed method for the phenols ranged from 0.15 to 0.38 μg/L. The recoveries measured by spiked samples at three concentration levels ranged from 81.6 to 99.3%, and precision was found with intra- and inter-day relative standard deviations less than 8.7 and 9.2%, respectively. Finally, the proposed method was successfully applied to the determination of the phenols in environmental water samples.

Solidified floating organic drop microextraction (SFODME) for the simultaneous analysis of three non-steroidal anti-inflammatory drugs in aqueous samples by HPLC

In this work, a liquid-liquid microextraction methodology using solidified floating organic drop (SFODME) was combined with liquid chromatography and UV/Vis detection to determine non-steroidal anti-inflammatory drugs (NSAIDs) naproxen (NPX), diclofenac (DCF), and mefenamic acid (MFN) in tap water, surface water, and seawater samples. Parameters that can influence the efficiency of the process were evaluated, such as the type and volume of the extractor and dispersive solvents, effect of pH, agitation type, and ionic strength. The optimized method showed low detection limits (0.09 to 0.25 μg L^-1), satisfactory recovery rates (90 to 116%), and enrichment factors in the range between 149 and 199. SFODME showed simplicity, low cost, speed, and high concentration capacity of the analytes under study. Its use in real samples did not demonstrate a matrix effect that would compromise the effectiveness of the method, being possible to apply it successfully in water samples with different characteristics.

Salting-out induced liquid-liquid microextraction for alogliptin benzoate determination in human plasma by HPLC/UV

Salting-out induced liquid–liquid microextraction method has been developed for plasma sample treatment before determination of alogliptin by high performance liquid chromatography with UV detection. Several parameters were optimized to achieve maximum enrichment, including type of extractant, volume of extractant, type of anion, type of cation, salt amount and pH. The optimum conditions were attained using 500 µL of acetonitrile, added to 1 mL of aqueous sample containing 250 mg of sodium chloride at pH 12. An RP-HPLC method was developed and validated according to the International Conference on Harmonization guidelines M10. The method was linear in the concentration range of 0.1 to 50 µg/mL (correlation coefficient = 0.997). The limit of detection was 0.019 µg/mL and limit of quantitation was 0.06 µg/mL. The method was accurate and precise with an average % recovery of 99.7% and a % relative standard deviation ranging between 1.5 and 2.5. These results showed that the salting-out induced liquid–liquid microextraction methods could be better than other sample preparation protocols in terms of sensitivity, easiness, solvent consumption and waste reduction.

Application of microextraction techniques in alternative biological matrices with focus on forensic toxicology: a review

The interest in alternative biological matrices (e.g., hair and saliva) for forensic toxicology analysis has increased, and recent developments in sample preparation have targeted rapid, cheap, efficient and eco-friendly methods, including microextraction techniques. For this review, we have gathered information about these two hot topics. We discuss the composition, incorporation of analytes and advantages and disadvantages of different biological matrices, and also present the operation principles of the most reported microextraction procedures and their application in forensic toxicology. The outcome of this review may encourage future forensic researches into alternative samples and microextraction techniques.