Extraction and stirring integrated techniques: examples and recent advances

Magnet Integrated Fabric Phase Sorptive Extraction for the Extraction of Resin Monomers from Human Urine Prior to HPLC Analysis

In this work, a method for the simultaneous determination of four resin monomers: Bisphenol A, bisphenol A methacrylate glycidate, triethyleneglycol-dimethacrylate, and urethane dimethacrylate, from human urine using magnet integrated fabric phase sorptive extraction (MI-FPSE), followed by high performance liquid chromatography (HPLC) diode array detection (HPLC-DAD), is presented. MI-FPSE is a novel configuration of FPSE that incorporates the stirring and extraction mechanism into one device, resulting in an improved extraction kinetic factor. FPSE is a green sample preparation technique that uses a flexible surface, such as cellulose, coated with a polymeric material using sol–gel technology. Poly(tetrahydrofuran) (PTHF) material was selected, due to its higher efficiency in terms of recovery rate among the studied MI-FPSE membranes. Optimization of the extraction process was performed based on several extraction and elution parameters. The method was validated for its linearity, selectivity, accuracy, precision, and stability of the samples. For the four compounds, the LOD and LOQ were 0.170 ng/μL and 0.050 ng/μL, respectively. The relative standard deviation of the method was less than 9.8% and 11.9%, for the within-day and between-day precision, respectively. The relative recoveries were between 85.6 and 105.2% in all cases, showing a good accuracy. The effectiveness of the proposed method was confirmed through successful application to the bioanalysis of real urine samples.

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.

Magnet integrated fabric phase sorptive extraction of selected endocrine disrupting chemicals from human urine followed by high-performance liquid chromatography - photodiode array analysis

In current paper, a new advanced modification of fabric phase sorptive extraction is introduced for the first time. This advantageous configuration that integrates the stirring and extraction mechanism into a single sample preparation device was originated by equally considering the beneficial role of the increase of extraction kinetics and more specifically of diffusion on the extraction efficiency of the equilibrium based microextraction techniques and the need for integrating and unite processes for better promotion and implementation of the principles of Green Analytical Chemistry. The resulted magnet integrated fabric phase sorptive extraction (MI-FPSE) device was the spearhead to develop a new analytical methodology for the determination of selected very common endocrine disrupting chemicals as model analytes in human urine by high-performance liquid chromatography-photodiode array analysis. More specifically, the sol-gel Carbowax 20 M coated on hydrophilic cellulose fabric substrate, MI-FPSE device was efficiently employed for the establishment of a new extraction protocol before the chromatographic determination. The sample preparation workflow was methodically optimized in terms of the elution solvent mixture, the volume of the sample, the extraction and the elution time, the stirring speed during the extraction, the ionic strength, and the pH of the sample matrix. The chromatographic separation was performed on a Spherisorb C18 column and a gradient elution program within 14 minutes. Mobile phase consisted of 0.05 ammonium acetate aqueous solution and acetonitrile. The method was validated towards linearity, sensitivity, selectivity, precision, accuracy, and stability. LOD and LOQ ranged between 1.05-1.80 and 3.5-6.0 ng/mL, while %RSD values were found lower than 9.0% in all cases. The method was efficiently applied to the bioanalysis of real samples. All the chosen EDCs were measured at high detection levels. The new MI-FPSE device has demonstrated its performance superiority as a magnet integrated stand-alone extraction device and could be considered as a significant improvement in the field of analytical/bioanalytical sample preparation.

Fabric Phase Sorptive Extraction: A Paradigm Shift Approach in Analytical and Bioanalytical Sample Preparation

Fabric phase sorptive extraction (FPSE) is an evolutionary sample preparation approach which was introduced in 2014, meeting all green analytical chemistry (GAC) requirements by implementing a natural or synthetic permeable and flexible fabric substrate to host a chemically coated sol-gel organic-inorganic hybrid sorbent in the form of an ultra-thin coating. This construction results in a versatile, fast, and sensitive micro-extraction device. The user-friendly FPSE membrane allows direct extraction of analytes with no sample modification, thus eliminating/minimizing the sample pre-treatment steps, which are not only time consuming, but are also considered the primary source of major analyte loss. Sol-gel sorbent-coated FPSE membranes possess high chemical, solvent, and thermal stability due to the strong covalent bonding between the fabric substrate and the sol-gel sorbent coating. Subsequent to the extraction on FPSE membrane, a wide range of organic solvents can be used in a small volume to exhaustively back-extract the analytes after FPSE process, leading to a high preconcentration factor. In most cases, no solvent evaporation and sample reconstitution are necessary. In addition to the extensive simplification of the sample preparation workflow, FPSE has also innovatively combined the extraction principle of two major, yet competing sample preparation techniques: solid phase extraction (SPE) with its characteristic exhaustive extraction, and solid phase microextraction (SPME) with its characteristic equilibrium driven extraction mechanism. Furthermore, FPSE has offered the most comprehensive cache of sorbent chemistry by successfully combining almost all of the sorbents traditionally used exclusively in either SPE or in SPME. FPSE is the first sample preparation technique to exploit the substrate surface chemistry that complements the overall selectivity and the extraction efficiency of the device. As such, FPSE indeed represents a paradigm shift approach in analytical/bioanalytical sample preparation. Furthermore, an FPSE membrane can be used as an SPME fiber or as an SPE disk for sample preparation, owing to its special geometric advantage. So far, FPSE has overwhelmingly attracted the interest of the separation scientist community, and many analytical scientists have been developing new methodologies by implementing this cutting-edge technique for the extraction and determination of many analytes at their trace and ultra-trace level concentrations in environmental samples as well as in food, pharmaceutical, and biological samples. FPSE offers a total sample preparation solution by providing neutral, cation exchanger, anion exchanger, mixed mode cation exchanger, mixed mode anion exchanger, zwitterionic, and mixed mode zwitterionic sorbents to deal with any analyte regardless of its polarity, ionic state, or the sample matrix where it resides. Herein we present the theoretical background, synthesis, mechanisms of extraction and desorption, the types of sorbents, and the main applications of FPSE so far according to different sample categories, and to briefly show the progress, advantages, and the main principles of the proposed technique.

Effervescence-Assisted Microextraction-One Decade of Developments

Dispersive microextraction techniques are key in the analytical sample treatment context as they combine a favored thermodynamics and kinetics isolation of the target analytes from the sample matrix. The dispersion of the extractant in the form of tiny particles or drops, depending on the technique, into the sample enlarges the contact surface area between phases, thus enhancing the mass transference. This dispersion can be achieved by applying external energy sources, the use of chemicals, or the combination of both strategies. Effervescence-assisted microextraction emerged in 2011 as a new alternative in this context. The technique uses in situ-generated carbon dioxide as the disperser, and it has been successfully applied in the solid-phase and liquid-phase microextraction fields. This minireview explains the main fundamentals of the technique, its potential and the main developments reported.

Chiral molecularly imprinted polymeric stir bar sorptive extraction for naproxen enantiomer detection in PPCPs

Chiral micropollutant analysis in pharmaceuticals and personal care products (PPCPs) is interesting but challenging. We firstly developed a series of chiral molecularly imprinted polymeric (CMIP) stir bar sorptive extraction coatings by combining a chiral template with chiral functional monomers via a click reaction for naproxen enantiomer analysis in PPCPs. Heterochiral selectivity was observed in the molecule recognition of the CMIP coatings, which demonstrated good adsorption capability for the chiral template and its structurally similar chiral compounds. The coatings also exhibited excellent enrichment capability for chiral analytes in an aqueous matrix. The surface morphology and pore structure of the CMIP coatings were characterized. The molecular interactions between the chiral template and chiral functional monomer were investigated through UV-vis spectroscopy and theoretical calculations to prove the effective interactions existing in the heterochiral MIPs. The CMIP coatings were used to enrich naproxen enantiomers in chiral drug and environmental water samples, and satisfactory recoveries (83.98 %-118.88 %) with a relative standard deviation of 3.49 %-13.08 % were achieved. The heterochiral imprinted coating-based method provided a sensitive, selective, and effective enrichment strategy for chiral micropollutant analysis in PPCPs. This technique is critical for chiral molecule recognition and enantiomer analysis in complex samples.

Synthesis, characterization, and application of chemically interconnected carbon nanotube monolithic sorbents by photopolymerization in polypropylene caps

A facile and convenient approach for the preparation of interconnected multiwalled carbon nanotube (MWCNT) monolithic sorbents in recycled plastic caps has been developed. The method, which was based on the photopolymerization of the individual MWCNTs via the formation of a W/O medium internal phase emulsion (40/60 w/w%), provides control over the size of pores, rigidity, and the mechanical stability of the final solid. Pluronic L121 was used as a surfactant containing the water phase inside it and, consequently, the organic and non-polar phase, in which the MWCNTs and the cross-linker were trapped, remained on the outside of the droplets. Optical microscopy and scanning electron microscopy (SEM) were employed to characterize the morphology of both the emulsions and the final solids, respectively. In addition, nitrogen intrusion porosimetry was performed in order to study how the specific surface area of the final monolithic solid changed (from 19.6 to 372.2 m² g^-1) with the variables involved in the polymerization step. To exemplify the great sorbent potential of the synthesized material, a colorimetric assay based on the retention of methylene blue within the interconnected MWCNT monolithic structure was carried out. Finally, following the positive results, the carbon nanotube-monolithic stirred caps were applied for the determination of chlorophenols in a biological matrix such as human urine, obtaining excellent recovery values (91-98%) and good precision (5.4-9.1%) under optimized extraction conditions. Graphical abstract.

Fabric Phase Sorptive Extraction Explained

The theory and working principle of fabric phase sorptive extraction (FPSE) is presented. FPSE innovatively integrates the benefits of sol–gel coating technology and the rich surface chemistry of cellulose/polyester/fiberglass fabrics, resulting in a microextraction device with very high sorbent loading in the form of an ultra-thin coating. This porous sorbent coating and the permeable substrate synergistically facilitate fast extraction equilibrium. The flexibility of the FPSE device allows its direct insertion into original, unmodified samples of different origin. Strong chemical bonding between the sol–gel sorbent and the fabric substrate permits the exposure of FPSE devices to any organic solvent for analyte back-extraction/elution. As a representative sorbent, sol–gel poly(ethylene glycol) coating was generated on cellulose substrates. Five (cm2) segments of these coated fabrics were used as the FPSE devices for sample preparation using direct immersion mode. An important class of environmental pollutants—substituted phenols—was used as model compounds to evaluate the extraction performance of FPSE. The high primary contact surface area (PCSA) of the FPSE device and porous structure of the sol–gel coatings resulted in very high sample capacities and incredible extraction sensitivities in a relatively short period of time. Different extraction parameters were evaluated and optimized. The new extraction devices demonstrated part per trillion level detection limits for substitute phenols, a wide range of detection linearity, and good performance reproducibility.

Ionic liquids intercalated in montmorillonite as the sorptive phase for the extraction of low-polarity organic compounds from water by rotating-disk sorptive extraction

Montmorillonite (MMT) clays were modified by the intercalation into their galleries of ionic liquids (IL) based on imidazolium quaternary ammonium salts. This new eco-materials exhibited good features for use as a sorptive phase in the extraction of low-polarity analytes from aqueous samples. Spectroscopic analyses of the modified clays were conducted and revealed an increase in the basal spacing and a shifting of the reflection plane towards lower values as a consequence of the effective intercalation of organic cations into the MMT structure. The novel sorbent developed herein was assayed as the sorptive phase in rotating-disk sorptive extraction (RDSE), using polychlorinated biphenyls (PCBs), representative of low-polarity pollutants, as model analytes. The final determination was made by gas chromatography with electron capture detection. Among the synthetized sorptive phases, the selected system for analytical purposes consisted of MMT modified with the 1-hexadecyl-3-methylimidazolium bromide (HDMIM-Br) IL. Satisfactory analytical features were achieved using a sample volume of 5 mL: the relative recoveries from a wastewater sample were higher than 80%, the detection limits were between 3 ng L^-1 and 43 ng L^-1, the precision (within-run precision) expressed as the relative standard deviation ranged from 2% to 24%, and the enrichment factors ranged between 18 and 28. Using RDSE, the extraction efficiency achieved for the selected MMT-HDMIM-Br phase was compared with other commercial solid phases/supports, such as polypropylene, polypropylene with 1-octanol (as a supported liquid membrane), octadecyl (C18) and octyl (C8), and showed the highest response for all the studied analytes. Under the optimized extraction conditions, this new device was applied in the analysis of the influent of a wastewater treatment plant in Santiago (Chile), demonstrating its applicability through the good recoveries and precision achieved with real samples.

Low-voltage electrochemically stimulated stir membrane liquid-liquid microextraction as a novel technique for the determination of methadone

In the present work, for the first time, a new portable setup was designed, developed and presented for the extraction of methadone, as a basic drug model from biological fluid samples using a low-voltage electrically stimulated stir membrane liquid-liquid microextraction technique (LV-ESSM-LLME), followed by high-performance liquid chromatography with ultraviolet detection. This new approach combines the advantages of stir membrane liquid-liquid microextraction and electrokinetic migration in the same unit under soft electrochemical conditions in a portable device, allowing for the isolation and preconcentration of the target analyte in a simple and efficient manner under three-phase mode. To investigate the influence of external stirring and the application of electrical potential as the driving force, a comparative study of all variables involved in the extraction process was carried out using the low-voltage electromembrane extraction (LV-EME) and LV-ESSM-LLME methods. Under soft electrokinetic migration conditions, methadone was transported from an acidic sample solution (pH 4.0), through the NPOE immobilized in the pores of the porous polypropylene sheet membrane, and into 25µL of 10mmolL^-1 HCl acceptor solution with a stirring rate of 1000rpm and 700rpm after 15min and 20min for LV-ESSM-LLME and LV-EME, respectively. Under the optimized conditions, preconcentration factors in the range of 17-24 and 21.5-29 for LV-EME and LV-ESSM-LLME, respectively, were considered, and satisfactory repeatability (4.5<[RSD]<7.5) was obtained in different matrices. The obtained relative recoveries of the target analyte were in the range of 87-94% and 93-101% for LV-EME and LV-ESSM-LLME, respectively, which indicated the excellent capability of the developed methods to extract methadone from complex matrices.

Glossary of terms used in extraction (IUPAC Recommendations 2016)

Approaches for analytical-scale extraction are developing rapidly as new strategies are implemented to improve sample throughput, to minimize material use in laboratory methods, and to develop on-site capabilities. In this contribution, definitions and recommendations for symbols for the terms used in analytical extraction are presented. Exhaustive, microextraction, elevated temperature, microwave- and ultrasound-assisted, parallel batch, flow through systems, and membrane extraction approaches are discussed. An associated tutorial titled “Extraction” provides a detailed introduction to the topic.

Assessment of commercially available polymeric materials for sorptive microextraction of priority and emerging nonpolar organic pollutants in environmental water samples

Among the different organic pollutants, persistent organic pollutants and emerging organic contaminants (EOCs) are of particular concern due to their potentially dangerous effects on the ecosystems and on human health. In the framework of the analysis of some of these organic pollutants in water samples, sorptive extraction devices have proven to be adequate for their monitoring. The efficiency of four commercially available and low-cost polymeric materials [polypropylene, poly(ethylene terephthalate), Raffia, and polyethersulfone (PES)] for the simultaneous extraction of 16 organic compounds from five different families from environmental water samples was evaluated in this work. Firstly, the homogeneity of the sorbent materials was confirmed by means of Raman spectroscopy. After the optimization of the parameters affecting the extraction and the liquid desorption steps, it was found that PES showed the largest efficiencies for slightly polar analytes and, to a lesser extent, for nonpolar analytes. Additionally, Raffia rendered good extraction efficiencies for nonpolar compounds. Thus sorptive extraction methods followed by large volume injection-programmable temperature vaporizer-gas chromatography-mass spectrometry were validated using PES and Raffia as sorbent materials. The validation of the method provided good linearity (0.978 < r (2) < 0.999 for PES and 0.977 < r (2) < 0.999 for Raffia), adequate repeatability (below 19 % and 14 % for PES and Raffia, respectively), and low method detection limits (low ng · l(-1) level). Finally, these materials were applied to the analysis of contaminants in environmental water samples.

Stir-membrane liquid microextraction for the determination of paracetamol in human saliva samples

Background: In this article, stir-membrane liquid microextraction is adapted for the analysis of volume-limited biological samples, using as a model analytical problem the determination of paracetamol in human saliva by LC with UV. A three-phase microextraction mode is used for the extraction of the target analyte, taking advantage of its acid–base properties. Results: All the variables involved in the extraction have been studied and optimized in depth. The method has been analytically characterized on the basis of its linearity, sensitivity and precision. The LOD is 0.5 µg/l while the repeatability, expressed as RSD, is better than 14.2 %. A tenfold preconcentration factor was obtained, which involves an absolute recovery value of 25%. Moreover, the relative recovery is very close to the 100%. Conclusion: Finally, the proposed method has been used to perform a PK study of paracetamol.

Novel sorption-based methodologies for static microextraction analysis: A review on SBSE and related techniques

Stir bar sorptive extraction (SBSE) became a well-established analytical technique in the last years, for which hundreds of applications in almost all types of scientific fields can be found in the literature. In spite of the great enrichment capacity and outstanding performance to operate at the ultra-trace level, this remarkable static sorption-based method is already not quite effective for some complex systems, in particular to monitor the large group of polar organic compounds. This review aims to cover the state-of-the-art in SBSE, as well as supplying a discussion of the analytical potential of the novel adsorptive microextraction techniques, as complementary enrichment approaches, by explaining the main principles and providing technical know-how for the beginners.