Single-drop microextraction

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 %.

Lab-made automated parallel-dispersive pipette extraction device for the determination of polycyclic aromatic hydrocarbons in distilled beverages (sugarcane spirits) using HPLC-DAD

This work describes the development of a new automated parallel dispersive tip microextraction method (Au-Pa-DPX) for the determination of eleven polycyclic aromatic hydrocarbons (PAHs) in four samples of Brazilian sugarcane spirit beverages, with separation and detection done by the HPLC-DAD. The results obtained with the Au-Pa-DPX approach were also compared with those obtained via the conventional parallel manual DPX method with the same samples and optimized extraction process. Desorption solvent and cycles of desorption, cleaning and extraction were optimized using response surface methodology and univariate approaches. For the Au-Pa-DPX method, the coefficient of determination (R2) ranged from 0.9948 to 0.9997. The limits of detection and quantification were all 0.303 μg l-1 and 1.00 μg l-1, respectively. Interday and intraday precision ranged from 7.6 % to 31.7 % and 0.40 % to 15.8 %, respectively. For the manual parallel DPX method, the interday and intraday precision ranged from 8.2 % to 38.1 % and 5.40 % to 18.7 %, respectively. The relative recovery values obtained with the proposed method ranged from 53.29 to 124.94 %. The enrichment factors ranged from 15.13 to 22.35. The sum of PAH concentrations in the four samples ranged from undetected to 25.58 μg l-1. These results, when correlated to other methods, highlight the gains in regards to precision obtained with the automated apparatus. Furthermore, when compared to other methods from the literature, it is an interesting green alternative for the determination of these analytes and this sample, with high throughput (4.67 min per sample), low consumption of solvents and samples, generating less waste and reducing health risks to the analyst.

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.

Nanoparticle Assisted Fabric Phase Sorptive Extraction for Azo Dye Determination in the Industrial Sewage

Currently, one of the significant environmental problems is the presence of azo dye materials in water sources. In this study, for the first time, a fast and sensitive sample preparation approach using nanoparticle-assisted fabric phase sorptive extraction (NFPSE) followed by high-performance liquid chromatography was examined to remove some azo dyes such as methyl red and sunset yellow from aqueous solutions. Primarily, the significance of several parameters affecting NFPSE, such as fabric type, the kind of sorbent, the number of contacts with sol-gel and the time of contact, was investigated. In addition, experiments were performed to determine the effect of different adsorption parameters, such as sample volume, adsorption time, adsorbent value, desorption time, ionic strength and pH. It was found that the calibration curve was linear within two ranges of concentrations (0.05-0.1 and 0.5-15 ng/L for methyl red; 0.05-0.5 and 0.5-15 ng/L for sunset yellow) with correlation coefficients better than 0.9683. The limit of detection was 0.014 ng/L for methyl red and 0.015 ng/L for sunset yellow. Repeatability Relative Standard Deviation (RSD) with three replicated experiments was 1.5-10% for methyl red and 2.5-5.8% for sunset yellow. Relative recovery percentages of 88-96% for methyl red and 62-92% for sunset yellow were obtained in the samples. Moreover, the results have shown that acceptable accuracy, precision and linearity make the "fabric phase sorptive extraction" a proper method for the determination of dyes from industrial sewage samples.

Synergy of Target-Induced Magnetic Network and Single-Drop Chromogenic System for Ultrasensitive "All-in-Tube" Detection of miRNA in Whole Blood

The development of liquid biopsy methods for the accurate and reliable detection of miRNAs in whole blood is critical for the early diagnosis and monitoring of diseases. However, accurate quantification of miRNA expression levels remains challenging due to the complex matrix and low abundance of miRNAs in blood samples. Herein, we report a contactless signal output strategy with low background interference that ensures "zero-contact" between the reaction system and the colorimetry system. The designed target-induced magnetic ZnS/ZIF-90/ZnS network can serve as a unique signal amplifier and transducer. It releases hydrogen sulfide (H2S) gas in an acidic solution which can be concentrated in a droplet of only a few microliters in volume, etching the silver layer of Au@Ag nanostars (NSTs) in the droplet. This will lead to changes in the localized surface plasmon resonance signals of the NSTs. Finally, quantitative detection of let-7a is realized by measuring the offset value of the UV-vis absorption peak. Therefore, by virtue of the synergistic action of quadruple signal amplification methods, including catalytic hairpin assembly, ZnS/ZIF-90/ZnS, magnetic separation, and microextraction, the "All-in-Tube" ultrasensitive detection of low-abundance let-7a in whole blood is achieved with a detection limit as low as the aM level. In addition, the "zero-contact" signal output mode effectively solves the problem of complex matrix interference, demonstrating the great potential of this method for miRNA quantification in complex samples, such as whole blood.

Enhancing Odor Analysis with Gas Chromatography-Olfactometry (GC-O): Recent Breakthroughs and Challenges

Gas chromatography-olfactometry (GC-O) has made significant advancements in recent years, with breakthroughs in its applications and the identification of its limitations. This technology is widely used for analyzing complex odor patterns. The review begins by explaining the principles of GC-O, including sample preparation, separation methods, and olfactory evaluation techniques. It then explores the diverse range of applications where GC-O has found success, such as food and beverage industries, environmental monitoring, perfume and aroma development, and forensic analysis. One of the major breakthroughs in GC-O analysis is the improvement in separation power and resolution of odorants. Techniques like rapid GC, comprehensive two-dimensional GC, and multidimensional GC have enhanced the identification and quantification of odor-active chemicals. However, GC-O also has limitations. These include the challenges in detecting and quantifying trace odorants, dealing with matrix effects, and ensuring the repeatability and consistency of results across laboratories. The review examines these limitations closely and discusses potential solutions and future directions for improvement in GC-O analysis. Overall, this review presents a comprehensive overview of the recent advances in GC-O, covering breakthroughs, applications, and limitations. It aims to promote the wider usage of GC-O analysis in odor analysis and related industries. Researchers, practitioners, and anyone interested in leveraging the capabilities of GC-O in analyzing complex odor patterns will find this review a valuable resource. The article highlights the potential of GC-O and encourages further research and development in the field.

Comparing π-complexation capabilities of ionic liquids containing silver(I) and copper(I) ions by headspace single drop microextraction in combination with high-performance liquid chromatography

Selective π-complexation capabilities of silver(I) and copper(I) ions can be effectively facilitated in ionic liquids. To understand the effects of environmental factors that influence the π-complexation of these metal ions with analytes, techniques that employ small volumes of ionic liquid that can be readily analyzed are desired. In this study, headspace single drop microextraction coupled with HPLC is used to investigate a diverse set of environmental factors on the metal ion-mediated complexation with aromatic compounds in ionic liquid media. Silver(I) and copper(I) bis[(trifluoromethyl)sulfonyl]imide salts were both studied by dissolving them in the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ionic liquid and employing the mixture as extraction media for aromatic compounds. Water and acetonitrile within the sample solution were observed to interfere with the complexation of silver(I) ions and aromatic compounds, while ethylene glycol and triethylene glycol did not. The temperature and extraction times were optimized to fully facilitate the π-complexation capabilities of metal ions in ionic liquid media. Partition coefficients between the sample headspace and metal ion were determined using a three-phase equilibria model. Although no discernable difference in analyte partitioning between the headspace and ionic liquid solvent was observed, analyte partition coefficients to silver(I) ion tended to be greater compared to copper(I) ion.

Matrix effects demystified: Strategies for resolving challenges in analytical separations of complex samples

Matrix effects can significantly impede the accuracy, sensitivity, and reliability of separation techniques presenting a formidable challenge to the analytical process. It is crucial to address matrix effects to achieve accurate and precise measurements in complex matrices. The multifaceted nature of matrix effects which can be influenced by factors such as target analyte, sample preparation protocol, composition, and choice of instrument necessitates a pragmatic approach when analyzing complex matrices. This review aims to highlight common challenges associated with matrix effects throughout the entire analytical process with emphasis on gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and sample preparation techniques. These techniques are susceptible to matrix effects that could lead to ion suppression/enhancement or impact the analyte signal at various stages of the analytical workflow. The assessment, quantification, and mitigation of matrix effects are necessary in developing any analytical method. Strategies can be implemented to reduce or eliminate the matrix effect by changing the type of ionization, improving extraction and clean-up methods, optimization of chromatography conditions, and corrective calibration methods. While development of an effective strategy to completely mitigate matrix effects remains elusive, an integrated approach that combines sample preparation, analytical extraction, and effective instrumental analysis remains the most promising avenue for identifying and resolving matrix effects.

Combination of headspace single-drop microextraction (HS-SDME) with a nickel-embedded paper-based analytical device for cyanide quantification

BACKGROUND

Cyanide anion can be found in foodstuffs, tobacco smoke and a variety of types of waters, mainly originating from anthropogenic activities. Due to its highly toxic nature, several agencies have established limits for cyanide levels in water. Additionally, monitoring cyanide levels in biological samples, such as blood and urine, is crucial for obtaining clinical information about the health condition of patients. Therefore, there is a pressing need for the development of simple, cost-effective, and reliable analytical methods capable of quantifying cyanide at low concentrations.

RESULTS

This study presents a novel analytical method for the selective and sensitive determination of cyanide based on analyte volatilization, pre-concentration via single-drop microextraction (SDME) using a selective reagent, and colorimetric quantification using a paper-based analytical device. For this, 10 mL of a liquid sample was acidified with phosphoric acid and the generated HCN was collected using a single drop of 3 μL of a palladium dimethylglyoximate solution (Pd (DMG)22-) positioned in the flask headspace using a syringe. The reaction of Pd (DMG)22- leads to the formation of Pd(CN)42- and the demasking of the organic ligand. After 15 min of extraction time, the reagent drop was added to a paper-based analytical device that has been previously impregnated with 3 μL of nickel chloride, resulting in the formation of a red precipitate of nickel (II) dimethylglyoximate. Digital images of the paper-based device were captured and the red channel (R) was used for quantification purposes. Under optimized conditions, the method demonstrates a suitable linear relation (r2 > 0.99) ranging from 26 to 286 μg L-1 and a limit of detection of 5 μg L-1.

SIGNIFICANCE

As a proof of concept, cyanide levels were quantified in water and urine samples using this method. The proposed approach offers high sensitivity and selectivity while requiring only a small volume of reagents. Furthermore, it exhibits a high degree of portability for in-situ applications.

Application of microfluidic technologies in forensic analysis

The application of microfluidic technology in forensic medicine has steadily expanded over the last two decades due to the favorable features of low cost, rapidity, high throughput, user-friendliness, contamination-free, and minimum sample and reagent consumption. In this context, bibliometric methods were adopted to visualize the literature information contained in the Science Citation Index Expanded from 1989 to 2022, focusing on the co-occurrence analysis of forensic and microfluidic topics. A deep interpretation of the literature was conducted based on co-occurrence results, in which microfluidic technologies and their applications in forensic medicine, particularly forensic genetics, were elaborated. The purpose of this review is to provide an impartial evaluation of the utilization of microfluidic technology in forensic medicine. Additionally, the challenges and future trends of implementing microfluidic technology in forensic genetics are also addressed.

Quantitative Time-Resolved Visualization of Catalytic Degradation Reactions of Environmental Pollutants by Integrating Single-Drop Microextraction and Fluorescence Sensing

Current methods for evaluating catalytic degradation reactions of environmental pollutants primarily rely on chromatography that often suffers from intermittent analysis, a long turnaround period, and complex sample pretreatment. Herein, we propose a quantitative time-resolved visualization method to evaluate the progress of catalytic degradation reactions by integrating sample pretreatment [single-drop microextraction, (SDME)], fluorescence sensing, and a smartphone detection platform. The dechlorination reaction of chlorobenzene derivatives was first investigated to validate the feasibility of this approach, in which SDME plays a critical role in direct sample pretreatment, and inorganic CsPbBr₃ perovskite encapsulated in a metal-organic framework (MOF-5) was utilized as the fluorescent chromogenic agent (FLCA) in SDME to realize fast in situ colorimetric detection via the color switching from green (CsPbBr₃) to blue (chlorine lead bromide, inorganic CsPbCl₃ perovskite). The smartphone, which can calculate the B/G value of FLCA, serves as a data output window for quantitative time-resolved visualization. Further, a [Eu(PMA)]_n (PMA= pyromellitic acid) fluorescent probe was constructed to use as an FLCA for the in situ evaluation of cinnamaldehyde and p-nitrophenol catalytic reduction. This approach not only minimizes the utilization of organic solvents and achieves quantitively efficient time-resolved visualization but also provides a feasible method for in situ monitoring of the progress of catalytic degradation reactions.

Headspace single drop microextraction based visual colorimetry for highly sensitive, selective and matrix interference-resistant determination of sulfur dioxide in food samples

Excessive intake of SO₂, a widely-used food additive, is able to cause respiratory, cardiovascular and neurological disease. For effectively monitoring SO₂ level, we have developed a headspace single drop microextraction based visual colorimetry for highly sensitive and selective sensing of SO₂ with TMB (3,3',5,5'-tetramethylbenzidine) as a classic chromogenic reagent. A combination of single drop and headspace microextraction integrated merits of high extraction efficiency, low consumption of reagents and excellent matrix interference-resistant ability. The colorimetric principle was based on oxidation of TMB, and SO₂ could compete with TMB to preferentially react with ·OH, resulting in the fading of color blue that could be easily read out by naked eye. LOD was calculated to be 0.53 μM and 5 μM by UV-vis and naked eye, respectively. The method was successfully utilized to analysis of food samples, and the experimental device was miniaturized and easy to construct, thus showing a promising potential in field analysis.

A rapid and green GC-MS method for the sampling of volatile organic compounds in spices and flowers by concurrent headspace single-drop microextraction and solid-phase microextraction

The equilibrium rather than the exhaustive nature of headspace single-drop microextraction (HS-SDME) and headspace solid-phase microextraction (HS-SPME) allowed the concurrent sampling of volatile organic compounds (VOCs) on the same sample in the same vial in a dual extraction configuration. This has avoided the necessity of conducting a separate set of experiments and was found to produce results in the time duration of a single sample preparation experiment. The results obtained by HS-SDME were validated against those found by the standard method of HS-SPME. Rectilinear calibration was made for certain VOCs tested as analytes over the range of 0.01-8 μg g^-1, and the average values of R², LOD and LOQ were found to be, respectively, 0.9992, 1.9 ng g^-1 and 5.7 ng g^-1 in HS-SDME, and 0.9991, 3.1 ng g^-1 and 9.1 ng g^-1 in HS-SPME. The spiked recoveries and RSD were, respectively, 100.5% and 3.3% in HS-SDME and 98.1% and 3.6% in HS-SPME. HS-SDME is convenient to perform and produce results in a much cheaper way than HS-SPME and free from the inconveniences of memory effects. With GC-MS, this method has also been implemented as a rapid, reliable and green procedure (by GAPI and AGREE tools) for the sampling of VOCs in real samples of spices, flowers, and a beetle nut chewing sample illicitly containing tobacco.

Spatial Confinement of Single-Drop System to Enhance Aggregation-Induced Emission for Detection of MicroRNAs

Due to high incidence, poor prognosis, and easy transformation into pancreatic cancer (PC) with high mortality, early diagnosis and prevention of acute pancreatitis (AP) have become significant research focuses. In this work, we proposed a magnetic single-drop microextraction (SDME) system with spatial confinement to enhance the aggregation-induced emission (AIE) effect for simultaneous fluorescence detection of miRNA-155 (associated with AP) and miRNA-196a (associated with PC). The target miRNAs were selectively recognized by the hairpin probe and triggered the DNA amplification reaction; then, the DNA strands with two independent probes of G-quadruplex/TAIN and Cy5 were constructed on the surfaces of the magnetic beads. The SDME process, in which a drop containing the fluorescence probes was formed at the tip of the magnetic microextraction rod rapidly within 10 s, was performed by magnetic extraction. In this way, G-quadruplex/TAIN was enriched owing to the spatial confinement of the single-drop system, and the fluorescence signal given off (by G-quadruplex/TAIN) was highly enhanced (AIE effect). This was detected directly by fluorescence spectrophotometry. The approach achieved low limits of detection of 2.1 aM for miRNA-196a and 8.1 aM for miRNA-155 and wide linear ranges from 10 aM to 10 nM for miRNA-196a and from 25 aM to 10 nM for miRNA-155. This novel method was applied to the fluorescence detection of miRNAs in human serum samples. High relative recoveries from 95.6% to 104.8% were obtained.

Determination of trace cobalt ions in bottled drinking water samples from Fiji Island by spray-assisted fine droplet formation-liquid phase microextraction based on simultaneous complexation and extraction before flame atomic absorption spectrometer measurement

In this study, a green, simple and effective preconcentration method named as spray-assisted fine droplet formation-liquid phase microextraction (SAFDF-LPME) before the flame atomic absorption spectrophotometry (FAAS) measurement for cobalt determination was developed. The method reduces the external dispersive solvent usage by using a simple spraying apparatus to obtain fine droplets of the extraction solvent. SAFDF-LPME method also consists of simultaneous complexation and extraction which indicates the environmental benevolence of the developed method. This method minimized the relative errors with high repeatability and accuracy by reducing the experimental steps. The influential parameters such as buffer type, buffer solution volume, extraction solvent/ligand solution volume (spraying cycle), and mixing period were systematically optimized by the univariate optimization procedure. With the optimum parameters applied, the detection power of the FAAS system was enhanced to about 110-folds with respect to 2.2 ng mL^-1 detection limit calculated for the proposed method. Bottled drinking water samples from Fiji Islands were used to demonstrate the applicability of the developed method for the accurate determination of trace cobalt in real sample matrices. Percent recovery results obtained between 95.5 and 88.5% showed the suitability of the developed method in the determination of cobalt at trace levels even in complex sample matrices.

Green bioanalysis: an innovative and eco-friendly approach for analyzing drugs in biological matrices

Green bioanalytical techniques aim to reduce or eliminate the hazardous waste produced by bioanalytical technologies. A well-organized and practical approach towards bioanalytical method development has an enormous contribution to the green analysis. The selection of the appropriate sample extraction process, organic mobile phase components and separation technique makes the bioanalytical method green. UHPLC-MS is the best option, whereas supercritical fluid chromatography is one of the most effective green bioanalytical procedures. Nevertheless, there remains excellent scope for further research on green bioanalytical methods. This review details the various sample preparation techniques that follow green analytical chemistry principles. Furthermore, it presents green solvents as a replacement for conventional organic solvents and highlights the strategies to convert modern analytical techniques to green methods.

Three-Dimensional Printed Microdevice to Enhance Headspace Microextraction for Enrichment of Histamine in Milk

In this work, a three-dimensional (3D) printed microdevice was designed to fix a drop of extractant that was applied to the enrichment of the most toxic biogenic amine, histamine, by headspace single-drop microextraction (HS-SDME). Concomitantly, based on the hybridization chain reaction of the histamine aptamer isothermal nucleic acid amplification strategy, a new fluorescence sensing method was developed to realize the highly sensitive detection of histamine. This is the first application of a 3D-printed microdevice to realize the HS-SDME process, which, among other advantages, effectively solves the problem of unstable and variable drop volumes that can plague traditional SDME and ensures the accuracy and repeatability of the extraction process. The calibration linear range of this SDME-fluorescence method was from 10 pM to 5 μM (R² > 0.98), and the limit of detection was as low as 3 pM. In addition, the method was successfully demonstrated to determine histamine spiked in milk, with recoveries of between 93% and 104%, and relative standard deviations of less than 5%. The method established in this study has important practical significance for food safety monitoring and human health and provides new ideas and solutions for the design and application of biosensors.

Overview of Different Modes and Applications of Liquid Phase-Based Microextraction Techniques

Liquid phase-based microextraction techniques (LPµETs) have attracted great attention from the scientific community since their invention and implementation mainly due to their high efficiency, low solvent and sample amount, enhanced selectivity and precision, and good reproducibility for a wide range of analytes. This review explores the different possibilities and applications of LPμETs including dispersive liquid–liquid microextraction (DLLME) and single-drop microextraction (SDME), highlighting its two main approaches, direct immersion-SDME and headspace-SDME, hollow-fiber liquid-phase microextraction (HF-LPME) in its two- and three-phase device modes using the donor–acceptor interactions, and electro membrane extraction (EME). Currently, these LPμETs are used in very different areas of interest, from the environment to food and beverages, pharmaceutical, clinical, and forensic analysis. Several important potential applications of each technique will be reported, highlighting its advantages and drawbacks. Moreover, the use of alternative and efficient “green” extraction solvents including nanostructured supramolecular solvents (SUPRASs, deep eutectic solvents (DES), and ionic liquids (ILs)) will be discussed.

Ionic Liquid-Assisted DLLME and SPME for the Determination of Contaminants in Food Samples

Developing effective and green methods for food analysis and separation has become an urgent issue regarding the ever-increasing concern of food quality and safety. Ionic liquids (ILs) are a new chemical medium and soft functional material developed under the framework of green chemistry and possess many unique properties, such as low melting points, low-to-negligible vapor pressures, excellent solubility, structural designability and high thermal stability. Combining ILs with extraction techniques not only takes advantage of ILs but also overcomes the disadvantages of traditional extraction methods. This subject has attracted intensive research efforts recently. Here, we present a brief review of the current research status and latest developments regarding the application of IL-assisted microextraction, including dispersive liquid–liquid microextraction (DLLME) and solid-phase microextraction (SPME), in food analysis and separation. The practical applications of ILs in determining toxic and harmful substances in food specimens with quite different natures are summarized and discussed. The critical function of ILs and the advantages of IL-based microextraction techniques over conventional extraction techniques are discussed in detail. Additionally, the recovery of ILs using different approaches is also presented to comply with green analytical chemistry requirements.

Lab-In-Syringe automation of deep eutectic solvent-based direct immersion single drop microextraction coupled online to high-performance liquid chromatography for the determination of fluoroquinolones

Lab-In-Syringe direct immersion single drop microextraction is proposed as an automated sample pretreatment methodology and coupled online to HPLC with fluorescence detection for the determination of fluoroquinolones in environmental waters. For the first time, a drop of a natural deep eutectic solvent (NADES), synthesized from hexanoic acid and thymol, has been used as an extractant in automated single-drop microextraction. The extraction procedure was carried out within the 5 mL void of an automatic syringe pump. A 9-position head valve served the aspiration of all required solutions, air, waste disposal, and hyphenation with the HPLC instrument. Sample mixing during extraction was done by a magnetic stirring bar placed inside the syringe. Only 60 μL of NADES were required omitting toxic classical solvents and improving the greenness of the proposed methodology. By direct injection, linear working ranges between 0.1 and 5 μg L^-1 were achieved for all fluoroquinolones. The limit of quantification values and enrichment factors ranged from 20 ng L^-1 to 30 ng L^-1 and 35 to 45, respectively. Accuracies obtained from the analysis of spiked surface water and wastewater treatment plant effluent analysis at two concentration levels (0.5 and 4 μg L^-1) ranged from 84.6% to 119.7%, with RSD values typically <3%.

Applications of surface-enhanced Raman spectroscopy in environmental detection

As the human population grows, the anthropogenic impacts from various agricultural and industrial processes produce unwanted contaminants in the environment. The accurate, sensitive and rapid detection of such contaminants is vital for human health and safety. Surface-enhanced Raman spectroscopy (SERS) is a valuable analytical tool with wide applications in environmental contaminant monitoring. The aim of this review is to summarize recent advancements within SERS research as it applies to environmental detection, with a focus on research published or accessible from January 2021 through December 2021 including early-access publications. Our goal is to provide a wide breadth of information that can be used to provide background knowledge of the field, as well as inform and encourage further development of SERS techniques in protecting environmental quality and safety. Specifically, we highlight the characteristics of effective SERS nanosubstrates, and explore methods for the SERS detection of inorganic, organic, and biological contaminants including heavy metals, pharmaceuticals, plastic particles, synthetic dyes, pesticides, viruses, bacteria and mycotoxins. We also discuss the current limitations of SERS technologies in environmental detection and propose several avenues for future investigation. We encourage researchers to fill in the identified gaps so that SERS can be implemented in a real-world environment more effectively and efficiently, ultimately providing reliable and timely data to help and make science-based strategies and policies to protect environmental safety and public health.

At-line coupling of hollow fiber liquid-phase microextraction to capillary electrophoresis for trace determination of acidic drugs in complex samples

Direct analysis of complex samples is demonstrated by the at-line coupling of hollow fiber liquid-phase microextraction (HF-LPME) to capillary electrophoresis (CE). The hyphenation of the preparative and the analytical technique is achieved through a 3D-printed microextraction device with an HF located in a sample vial of a commercial CE instrument. The internal geometry of the device guides the CE separation capillary into the HF and the CE injection of the HF-LPME extract is performed directly from the HF lumen. The 3D-printing process ensures uniform dimensions of the devices, their constant position inside the sample vial, and excellent repeatability of the HF-LPME as well as the CE injection. The devices are cheap (∼0.01 €) and disposable, thus eliminating any possible sample-carryover, moreover, the at-line CE analysis of the extract is performed fully autonomously with no need for operator's intervention. The developed HF-LPME/CE-UV method is applied to the determination of acidic drugs in dried blood spot and wastewater samples and is characterized by excellent repeatability (RSD, 0.6-9.6%), linearity (r², 0.9991-0.9999), enrichment (EF, 29-97), sensitivity (LOD, 0.2-3.4 μg/L), and sample throughput (7 samples/h). A further improvement of selected characteristics of the analytical method is achieved by the at-line coupling of HF-LPME to capillary isotachophoresis (ITP) with electrospray ionization-mass spectrometry (ESI-MS). The HF-LPME/ITP-ESI-MS system facilitates enhanced selectivity, matrix-free analytical signals, and up to 34-fold better sensitivity due to the use of ESI-MS detection and additional on-capillary ITP preconcentration of the HF-LPME extracts.

Single-drop microextraction technique for the determination of antibiotics in environmental water

Growing concerns related to antibiotic residues in environmental water have encouraged the development of rapid, sensitive, and accurate analytical methods. Single-drop microextraction has been recognized as an efficient approach for the isolation and preconcentration of several analytes from a complex sample matrix. Thus, single-drop microextraction techniques are cost-effective and less harmful to the environment, subscribing to green analytical chemistry principles. Herein, an overview and the current advances in single-drop microextraction for the determination of antibiotics in environmental water are presented were included. In particular, two main approaches used to perform single-drop microextraction (direct immersion-single-drop microextraction and headspace-single-drop microextraction) are reviewed. Furthermore, the impressive analytical features and future perspectives of single-drop microextraction are discussed in this review. This article is protected by copyright. All rights reserved.

Single bubble in-tube microextraction coupled with capillary electrophoresis

Headspace (HS) extraction is a sample pretreatment technique for volatile and semivolatile organic compounds in a complex matrix. Recently, in-tube microextraction (ITME) coupled with CE using an acceptor plug placed in the capillary inlet was developed as a simple but powerful HS extraction method. Here, we present single bubble (SB) ITME using a bubble hanging to the capillary inlet immersed in a sample donor solution as a HS of submicroliter volume (∼200 nL). The analytes evaporated to the bubble were extracted into the acceptor phase through the capillary opening, then electrophoresis of the enriched extract was carried out. Since the bubble volume was much smaller than a conventional HS volume (∼1 mL), it was filled with the evaporated analytes rapidly and the analytes could be enriched much faster compared to conventional HS-ITME. Owing to the high surface-to-volume ratio of the SB, 5 min SB-ITME yielded the enrichment factor values similar to those of 10 min HS-ITME. When 5 min SB-ITME at room temperature was applied to a tap water sample, the enrichment factors of 2,4,6-trichlorophenol (TCP), 2,3,6-TCP, and 2,6-dichlorophenol were 53, 41, and 60, respectively, and the LOQs obtained by monitoring the absorbance at 214 nm were 5.6-8.3 ppb, much lower than 200 ppb, the World Health Organization guideline for the maximum permissible concentration of 2,4,6-TCP in drinking water.

Facile and highly efficient three-phase single drop microextraction in-line coupled with capillary electrophoresis

A high-performance version of in-line, three-phase direct immersion-single drop microextraction (DI-SDME) coupled with capillary electrophoresis (CE) was demonstrated using a commercial CE instrument, and all the major and minor details were described to provide an easy-to-follow and user-friendly protocol. The excellent sample cleanup and enrichment power of this method was demonstrated with nonsteroidal anti-inflammatory drugs (NSAIDs) in human urine. The only preparation of urine samples was the addition of HCl to acidify the urine sample to pH 2. The acidic NSAIDs in the acidified urine sample were extracted into a basic acceptor drop covered with a thin organic layer attached to the inlet tip of a capillary immersed in the sample. A simple but powerful DI-SDME-CE method could be carried out automatically without any modification of the existing CE instrument. For improved performance, sample agitation and heating were employed by installing a microstirrer and a thermostating jacket in the sample tray. With 10 min of DI-SDME at 35°C with stirring, NSAIDs such as ketoprofen, ibuprofen, and naproxen in urine were enriched 340-970-fold with intraday and interday RSDs of 0.8-2.4% and 1.1-3.6%, respectively. The LODs obtained with in-line coupled CE/UV were 10-50 nM (2-10 µg/L). The performance of DI-SDME-CE/UV was also demonstrated by determining the naproxen level in human urine collected 24 h after taking a single oral dose of the drug. The spike recovery of naproxen from a single-point standard addition to the urine sample was 80%. Our high-performance three-phase DI-SDME-CE method is quite promising for the analysis of ionizable trace analytes in a complex sample matrix.

Current overview and perspectives in environmentally friendly microextractions of carbamates and dithiocarbamates

Carbamates and dithiocarbamates are two classes of pesticides widely employed in the agriculture practice to control and avoid pests and weeds, hence, the monitoring of the residue of those pesticides in different foodstuff samples is important. Thus, this review presents the classification, chemical structure, use, and toxicology of them. Moreover, it was shown the evolution of liquid- and solid-phase microextractions employed in the extraction of carbamates and dithiocarbamates in water and foodstuff samples. The classification, operation mode, and application of the microextractions of liquid-phase and solid-phase used in their extraction were discussed and related to the analytical parameters and guidelines of green analytical chemistry.

Recent advances in the chromatographic determination of the most commonly used anti-hepatitis C drug sofosbuvir and its co-administered drugs in human plasma

Sofosbuvir is a direct-acting antiviral drug that inhibits hepatitis C virus (HCV) NS5B polymerase, which in turn affects the virus replication inside biological systems. The clinical importance of sofosbuvir is based not only on its effect on HCV but also on other lethal viruses such as Zika and severe acute respiratory syndrome coronavirus disease 2019 (SARS-COVID-19). Accordingly, there is a continuous shedding of light on the development and validation of accurate and fast analytical methods for the determination of sofosbuvir in different environments. This work critically reviews the recent advances in chromatographic methods for the analysis of sofosbuvir and/or its metabolites in pure samples, pharmaceutical dosage forms, and in the presence of other co-administered drugs to highlight the current status and future perspectives to enhance its determination in different matrixes.

Development of a deep eutectic solvent-based ultrasound-assisted homogenous liquid-liquid microextraction method for simultaneous extraction of daclatasvir and sofosbuvir from urine samples

An ultrasound-assisted homogenous liquid-liquid microextraction method using a new deep eutectic solvent was proposed for the extraction of daclatasvir and sofosbuvir from urine. The analytes were determined by high performance liquid chromatography-diode array detector. The deep eutectic solvent was prepared by mixing p-aminophenol with tetrabutyl ammonium chloride. It was used in the extraction procedure as an extraction solvent. The amine group in structure of the prepared deep eutectic solvent led to its various solubility in different pHs. In this method, urine sample was placed in a glass test tube and then mixed with sodium chloride and its temperature adjusted at 50 °C. Then, the deep eutectic solvent was dissolved in the solution by manually shaking. In the following, an ammonia solution was added to the solution and the mixture was sonicated for 4 min. After centrifugation, an aliquat of the sedimented phase was injected into the determination system. Low limits of detection (daclatasvir 1.0 and sofosbuvir 1.3 μg/L) and quantification (daclatasvir 3.3 and sofosbuvir 4.0 μg/L), high enrichment factor (daclatasvir 96 and sofosbuvir 90) and extraction recovery (daclatasvir 96 and sofosbuvir 90 %), and good percision (relative standard deviation ≤9.3 %) were obtained. The introduced method was successfully applied in the determination of daclatasvir and sofosbuvir concentrations in urine samples.

Surface nanodroplet-based nanoextraction from sub-milliliter volumes of dense suspensions

A greener analytical technique for quantifying compounds in dense suspensions is needed for wastewater and environmental analysis, chemical or bio-conversion process monitoring, biomedical diagnostics, and food quality control, among others. In this work, we introduce a green, fast, one-step method called nanoextraction for extraction and detection of target analytes from sub-milliliter dense suspensions using surface nanodroplets without toxic solvents and pre-removal of the solid contents. With nanoextraction, we achieve a limit of detection (LOD) of 10-9 M for a fluorescent model analyte obtained from a particle suspension sample. The LOD is lower than that in water without particles (10-8 M), potentially due to the interaction of particles and the analyte. The high particle concentration in the suspension sample, thus, does not reduce the extraction efficiency, although the extraction process was slowed down up to 5 min. As a proof of principle, we demonstrate the nanoextraction for the quantification of model compounds in wastewater slurry containing 30 wt% solids and oily components (i.e. heavy oils). The nanoextraction and detection technology developed in this work may be used in fast analytical technologies for complex slurry samples in the environment, industrial waste, or in biomedical diagnostics.

Microdroplet extraction assisted ultrasensitive Raman detection in complex oil

The Raman detection of trace substances in complex oil is still a great challenge at present because of the strong disturbance of background activity and the suppression of intensity in spectra caused by complicated components. In this work, a simple and robust approach based on microdroplet liquid-liquid extraction for the real-time Raman spectroscopy monitoring of trace substances in complex oil is reported. Based on unbalanced chemical potentials between water and oil on a microfluidic chip, a target trace molecule is extracted from complex mineral oil to a water microdroplet. Benefiting from the real-time fluorescence intensities of fluorescein in a water microdroplet, the extraction performance is investigated and optimized. The optimal water microdroplet is implemented for the Raman detection of furfural in a complex mineral oil, a typical trace performance marker in electric power equipment, and this exhibits excellent sensitivity with a limit of detection (LOD) of 26 ppb. Compared to traditional detection technology for trace substances in complex oil (high performance liquid chromatography, HPLC), this method greatly simplified the process of measurement, reduced the volume of sample required, had a fast measurement time, and exhibited the prospect of real-time monitoring applications with high sensitivity, which not only promotes the development of oil quality but also enlarges existing knowledge related to using Raman spectroscopy in chem-/bio-sensing.

A computational simulation of electromembrane extraction based on Poisson - Nernst - Planck equations

Electromembrane extraction (EME) has attracted a great deal of interest in researchers because of its advantages. For analysis, design and optimization purposes, understanding the ion transport mechanisms in the organic supported liquid membrane (SLM) is of prominent importance, where the interplay between the passive diffusion and electric-driven mass transport across SLM affects the mass transfer. In present work, a 2D numerical simulation is developed to examine the mass transfer behavior and the analyte recovery in EME devices. The presented model is capable of describing the effect of different parameters on the recovery of the EME setup. Initial analyte concentration in the sample solution, SLM thickness, applied potential, permittivity, diffusion coefficient, and the reservoir pH within both the sample and acceptor, can be considered as process variables. Predicted results revealed that the most important factors playing key role in EME, are the analyte diffusivity, distribution coefficient of the analyte as well as the level of protonation in both the donor and acceptor solutions. The proposed model is helpful in predicting the mass transfer behavior of the EME process in practical applications.

Recent applications of microextraction sample preparation techniques in biological samples analysis

Analysis of biological samples is affected by interfering substances with chemical properties similar to those of the target analytes, such as drugs. Biological samples such as whole blood, plasma, serum, urine and saliva must be properly processed for separation, purification, enrichment and chemical modification to meet the requirements of the analytical instruments. This causes the sample preparation stage to be of undeniable importance in the analysis of such samples through methods such as microextraction techniques. The scope of this review will cover a comprehensive summary of available literature data on microextraction techniques playing a key role for analytical purposes, methods of their implementation in common biological samples, and finally, the most recent examples of application of microextraction techniques in preconcentration of analytes from urine, blood and saliva samples. The objectives and merits of each microextration technique are carefully described in detail with respect to the nature of the biological samples. This review presents the most recent and innovative work published on microextraction application in common biological samples, mostly focused on original studies reported from 2017 to date. The main sections of this review comprise an introduction to the microextraction techniques supported by recent application studies involving quantitative and qualitative results and summaries of the most significant, recently published applications of microextracion methods in biological samples. This article considers recent applications of several microextraction techniques in the field of sample preparation for biological samples including urine, blood and saliva, with consideration for extraction techniques, sample preparation and instrumental detection systems.

Miniaturized sample preparation techniques and ambient mass spectrometry as approaches for food residue analysis

Analytical methods such as liquid chromatography (LC) and mass spectrometry (MS) are widely used techniques for the analyses of different classes of compounds. This is due to their highlighted capacity for separating and identifying components in complex matrices such food samples. However, in most cases, effective analysis of the target analyte becomes challenging due to the complexity of the sample, especially for quantification of trace concentrations. In this case, miniaturized sample preparation methods have been used as a strategy for analysis of complex matrices. This involves removing the interferents and concentrating the analytes in a sample. These methods combine simplicity and effectiveness and given their miniaturized scale, they are in accordance with green chemistry precepts. Besides, ambient mass spectrometry represents a new trend in fast and rapid analyses, especially for qualitative and screening analysis. However, for complex matrix analyses, sample preparation is still a difficult step and the miniaturized sample preparation techniques show great potential for an improved and widespread use of ambient mass spectrometry techniques. . This review aims to contribute as an overview of current miniaturized sample preparation techniques and ambient mass spectrometry methods as different approaches for selective and sensitive analysis of residues in food samples.