Electromembrane extraction

A new coaxial flow-through probe for electromembrane extraction of methadone from clinical samples on-line coupled to capillary electrophoresis

BACKGROUND

A new design of a flow-through coaxial electromembrane extraction (EME) probe that can be on-line coupled with CE instrument is described and tested. The supporting base of the probe is a PDMS microchip with T-shaped channels into which two coaxially arranged capillaries for inlet and outlet solutions are inserted. The extraction part of the probe is a porous polypropylene hollow fiber, sealed at one end and modified with nitrophenyloctyl ether (NPOE) extraction fluid. The internal volume of the extraction probe is 1.1 μL.

RESULTS

The EME probe was tested on laboratory samples and methadone was extracted into 3.0 M AcOH as acceptor. The concentration dependence was linear in the range of 0.1-1.0 μg mL-1 at EME 300 s/150 V and in the range of 0.5-10.0 μg mL-1 at EME 100 s/150 V. The enrichment factor was greater than 30 and the LOD was 0.21 μg mL-1. The EME of methadone in clinical samples showed a linear concentration dependence in human urine and a nonlinear concentration dependence in serum. The distribution of methadone in each phase of the extraction system and the effect of extraction membrane thickness on the enrichment factor were studied. The EME probe can be applied repeatedly.

SIGNIFICANCE

The supporting base of EME probe and flow gating interface (FGI) are realized by a microfluidic PDMS microchips cast in the laboratory without the use of lithography. A supporting PDMS chip with coaxially arranged capillaries and extraction membrane forms a compact analytical instrument. The entire EME/CE analysis process is performed on a laboratory-made instrument and automated by LabView.

3D-printed stereolithographic fluidic devices for automatic nonsupported microelectromembrane extraction and clean-up of wastewater samples

BACKGROUND

There is a quest of novel functional and reliable platforms for enhancing the efficiency of microextraction approaches in troublesome matrices, such as industrial wastewaters. 3D printing has been proven superb in the analytical field to act as the springboard of microscale extraction approaches.

RESULTS

In this work, low-force stereolithography (SL) was exploited for 3D printing and prototyping bespoke fluidic devices for accommodating nonsupported microelectromembrane extraction (μEME). The analytical performance of 3D-printed μEME devices with distinct cross-sections, including square, circle, and obround, and various channel dimensions was explored against that of commonly used circular polytetrafluoroethylene (PTFE) tubing in flow injection systems. A computer-controlled millifluidic system was harnessed for the (i) automatic liquid-handling of minute volumes of donor, acceptor, and organic phases at the low μL level that spanned from 3 to 44 μL in this work, (ii) formation of three-phase μEME, (iii) in-line extraction, (iv) flow-through optical detection of the acceptor phase, and (v) solvent removal and regeneration of the μEME device and fluidic lines. Using methylene blue (MB) as a model analyte, experimental results evinced that the 3D-printed channels with an obround cross-section (2.5 mm × 2.5 mm) were the most efficient in terms of absolute extraction recovery (59%), as compared to PTFE tubing of 2.5 mm inner diameter (27%). This is attributed to the distinctive convex interface of the organic phase (1-octanol), with a more pronounced laminar pattern, in 3D-printed SL methacrylate-based fluidic channels against that of PTFE tubing on account of the enhanced 1-octanol wettability and lower contact angles for the 3D-printed devices. The devices with obround channels were leveraged for the automatic μEME and in-line clean-up of MB in high matrix textile dyeing wastewater samples with relative recoveries ≥81%, RSD% ≤ 17.1% and LOD of 1.3 mg L-1. The 3D-printed nonsupported μEME device was proven superb for the analysis of wastewater samples with an elevated ionic strength (0.7 mol L-1 NaCl, 5000 mg L-1 Na2CO3, and 0.013 mol L-1 NaOH) with recorded electric currents below 12 μA.

NOVELTY

The coupling of 3D printing with nonsupported μEME in automatic flow-based systems is herein proposed for the first time and demonstrated for the clean-up of troublesome samples, such as wastewaters.

Comparison of the applicability of electromembrane extraction and liquid-phase microextraction for extraction of non-polar basic drugs from different biological samples: Using clozapine as the model analyte

Understanding and comparing the applicability of electromembrane extraction (EME) and liquid-phase microextraction (LPME) is crucial for selecting an appropriate microextraction approach. In this work, EME and LPME based on supported liquid membranes were compared using biological samples, including whole blood, urine, saliva, and liver tissue. After optimization, efficient EME and LPME of clozapine from four biological samples were achieved. EME provided higher recovery and faster mass transfer for blood and liver tissue than LPME. These advantages were attributed to the electric field disrupting clozapine binding to interfering substances. For urine and saliva, EME demonstrated similar recoveries while achieving faster mass transfer rates. Finally, efficient EME and LPME were validated and evaluated combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The coefficient of determination of all methods was greater than 0.999, and all methods showed acceptable reproducibility (≤14%), accuracy (90%-110%), and matrix effect (85%-112%). For liver and blood with high viscosity and complex matrices, EME-LC-MS/MS provided better sensitivity than LPME-LC-MS/MS. The above results indicated that both EME and LPME could be used to isolate non-polar basic drugs from different biological samples, although EME demonstrated higher recovery rates for liver tissue and blood.

Green strategies using solvent-free biodegradable membranes in microfluidic devices. Liquid phase microextraction and electromembrane extraction

In this work, a novel solvent-free microfluidic method based liquid phase microextraction has been proposed for the first time. A comprehensive study of liquid phase microextraction (LPME) and electromembrane extraction (EME) implemented in microfluidic formats has been carried out to investigate the efficiency of biodegradable membranes (such as agarose) without organic solvent to develop fully environmental microfluidic methods. For this study, non-polar and polar basic compounds (five) were selected as model analytes and different agarose membrane compositions were synthesized and tested with and without organic solvent (solvent-free). Under optimal experimental conditions, the extraction efficiencies obtained using solvent-free LPME-chip devices were similar to the ones obtained using solvent-free EME-chip devices at very low voltages (0.25 V), however, LPME microfluidic format was selected due to its simplicity. The proposed green microfluidic device was successfully applied in urine samples with recoveries between 80 and 93% for all analytes and relative standard deviation below 7% for all analytes. Results were compared with experiments previously conducted using conventional (polypropylene) membranes, observing that solvent-free microfluidic systems based on biodegradable solid support materials have proven to be an attractive alternative and offered the same advantages in terms of membrane stability allowing consecutive extractions compared to supported liquid membranes (SLM) microfluidic methods.

Solar energy-based electromembrane extraction using agarose gel for the determination of nonsteroidal anti-inflammatory drugs from biological samples: An environmentally friendly strategy

This paper presents the application of solar energy as a renewable resource in gel electromembrane extraction (G-EME). The extraction driving force (electrical field) generated from solar energy is stored through photovoltaic panels and significantly contributes to reducing the emission of greenhouse gasses. Moreover, the replacement of the polypropylene membrane and organic extracting solvents with biodegradable agarose membrane and the aqueous extracting solutions makes the presented approach compatible with the principles of green chemistry. Naproxen (NAP) and ibuprofen (IBF) were extracted from urine samples to the aqueous acceptor phase containing an anode electrode situated on the other side of the agarose gel membrane. Acceptable linearity was obtained in the concentration ranges of 6-100 and 9-100 μg. L - 1 with detection limits of 2 and 3 μg. L - 1 for NAP and IBF, respectively.

Conductive vial electromembrane extraction of opioids from oral fluid

The use of oral fluid as sample matrix has gained significance in the analysis of drugs of abuse due to its non-invasive nature. In this study, the 13 opioids morphine, oxycodone, codeine, O-desmethyl tramadol, ethylmorphine, tramadol, pethidine, ketobemidone, buprenorphine, fentanyl, cyclopropylfentanyl, etonitazepyne, and methadone were extracted from oral fluid using electromembrane extraction based on conductive vials prior to analysis with ultra-high performance liquid chromatography-tandem mass spectrometry. Oral fluid was collected using Quantisal collection kits. By applying voltage, target analytes were extracted from oral fluid samples diluted with 0.1% formic acid, across a liquid membrane and into a 300 μL 0.1% (v/v) formic acid solution. The liquid membrane comprised 8 μL membrane solvent immobilized in the pores of a flat porous polypropylene membrane. The membrane solvent was a mixture of 6-methylcoumarin, thymol, and 2-nitrophenyloctyl ether. The composition of the membrane solvent was found to be the most important parameter to achieve simultaneous extraction of all target opioids, which had predicted log P values in the range from 0.7 to 5.0. The method was validated in accordance to the guidelines by the European Medical Agency with satisfactory results. Intra- and inter-day precision and bias were within guideline limits of ± 15% for 12 of 13 compounds. Extraction recoveries ranged from 39 to 104% (CV ≤ 23%). Internal standard normalized matrix effects were in the range from 88 to 103% (CV ≤ 5%). Quantitative results of authentic oral fluid samples were in accordance with a routine screening method, and external quality control samples for both hydrophilic and lipophilic compounds were within acceptable limits.

Impact of a Whey Protein Hydrolysate Treated by Electrodialysis with Ultrafiltration Membrane on the Development of Metabolic Syndrome and the Modulation of Gut Microbiota in Mice

The development of Metabolic Syndrome (MetS) affects a large number of people around the world and represents a major issue in the field of health. Thus, it is important to implement new strategies to reduce its prevalence, and various approaches are currently under development. Recently, an eco-friendly technology named electrodialysis with ultrafiltration membrane (EDUF) was used successfully for the first time at a semi-industrial scale to produce three fractions concentrated in bioactive peptides (BPs) from an enzymatically hydrolyzed whey protein concentrate (WPC): the initial (F1), the final (F2) and the recovery fraction (F3), and it was demonstrated in vitro that F3 exhibited interesting DPP-IV inhibitory effects. Therefore, the present study aimed to evaluate the effect of each fraction on in vivo models of obesity. A daily dose of 312.5 mg/kg was administered to High Fat/High Sucrose diet (HFHS) induced C57BL6/J mice for eight weeks. The physiological parameters of each group and alterations of their gut microbiota by the fractions were assessed. Little effect of the different fractions was demonstrated on the physiological state of the mice, probably due to the digestion process of the BP content. However, there were changes in the gut microbiota composition and functions of mice treated with F3.

Technological advances for analyzing the content of organ-on-a-chip by mass spectrometry

Three-dimensional (3D) cell cultures, including organ-on-a-chip (OOC) devices, offer the possibility to mimic human physiology conditions better than 2D models. The organ-on-a-chip devices have a wide range of applications, including mechanical studies, functional validation, and toxicology investigations. Despite many advances in this field, the major challenge with the use of organ-on-a-chips relies on the lack of online analysis methods preventing the real-time observation of cultured cells. Mass spectrometry is a promising analytical technique for real-time analysis of cell excretes from organ-on-a-chip models. This is due to its high sensitivity, selectivity, and ability to tentatively identify a large variety of unknown compounds, ranging from metabolites, lipids, and peptides to proteins. However, the hyphenation of organ-on-a-chip with MS is largely hampered by the nature of the media used, and the presence of nonvolatile buffers. This in turn stalls the straightforward and online connection of organ-on-a-chip outlet to MS. To overcome this challenge, multiple advances have been made to pre-treat samples right after organ-on-a-chip and just before MS. In this review, we summarised these technological advances and exhaustively evaluated their benefits and shortcomings for successful hyphenation of organ-on-a-chip with MS.

An improved microfluidic device to enhance the enrichment factors in liquid phase microextraction: application to the simultaneous extraction of polar and non-polar acids in biological samples

A new microfluidic device to enhance the enrichment factor in miniaturized systems is proposed. The microfluidic system was design for liquid phase microextractions, and it was applied to the simultaneous extraction of acidic compounds of a wide range of polarity (0.5 < log P < 3). The device operated under stagnant acceptor phase conditions and all the operational parameters involved were optimized. Tributyl phosphate was found to be a new highly efficient supported liquid membrane to simultaneously extract analytes of very different polarities. The optimal donor and acceptor phase were pH 2 and pH 13, respectively. The donor flow rate and the extraction time were investigated simultaneously, offering great versatility with high enrichment factors (EFs). Limits of quantitation were within 0.02 and 0.09 µg mL^-1 for all compounds at 10 µL min^-1 as donor flow rate and 20-min extractions, offering EFs between 11 and 18 with only 200-µL sample volume consumption. The method was successfully applied to human urine samples, observing recoveries between 47 and 90% for all compounds. This new proposed microfluidic system increases the wide range of applications, especially when the analytes are present in lower concentrations in the sample.

Multiphase electroextraction as a simple and fast sample preparation alternative for the digital image determination of doxorubicin in saliva

Monitoring chemotherapeutic drugs in biological fluids is, in many cases, extremely important for dose adjustment, the maintenance of therapies, and the control of side effects. In this work, a method for determining the doxorubicin in saliva by digital image analysis (DIA) was optimised and validated. Images from a paper point were obtained using a conventional and cheap flatbed scanner at a 600 ppp resolution. The RGB data channels were obtained from the images in a region of 15 × 15 pixels around the sorbent vertex. The paper point was used as sorbent material in sample preparation using a multiphase electroextraction system. Following optimisation using a Doehlert experimental design, the method was able to simultaneously extract 66 samples in 20 min. The high selectivity of the electric field associated with the sorption capacity of the cellulosic material allowed the chemotherapy drug to be pre-concentrated and quantified in a range between 50 and 500 μg L^-1 (R² > 0.98). The method also exhibited adequate parameters (limits of detection and quantification, recovery, and precision) indicating its potential application in the monitoring of doxorubicin and similar drugs in saliva.

A new electromembrane extraction probe for on-line connection with capillary electrophoresis for determination of substances in biological matrices

A miniature probe for electromembrane extraction is developed and constructed. The tubular probe with an internal volume of 1.1 μL is made of polypropylene hollow fiber with a supported liquid membrane of 85% nitrophenyloctyl ether (NPOE) with 15% bis(2-ethylhexyl)phosphonic acid (DEHP). The probe is connected on-line to the electrophoresis with short separation capillary via an air assisted flow gating interface cast from poly (dimethylsiloxane). The compact instrument is computer controlled via LabView. The probe parameters are tested for extraction of creatinine and basic amino acids from artificial solution and human urine. The sensitivity of the electrophoretic determination after 300 s extraction at 150 V compared to the sensitivity without extraction is 4.9-fold and 2.6-fold higher for creatinine and arginine, respectively. The RSDs for peak area measured from 5 repeated extractions of 50 μM solutions are 7.5%, 7.2%, 8.6% and 9.2% for Crea, Lys, Arg and His, respectively. The probe can be used for all-day measurements. The preparation of the probe is simple and requires no special tool.

Solid supports and supported liquid membranes for different liquid phase microextraction and electromembrane extraction configurations. A review

Liquid phase microextraction (LPME) and electromembrane microextraction (EME) can be considered as two of the most popular techniques in sample treatment today. Both techniques can be configurated as membrane-assisted techniques to carry out the extraction. These supports provide the required geometry and stability on the contact surface between two phases (donor and acceptor) and improve the reproducibility of sample treatment techniques. These solid support pore space, once is filled with organic solvents, act as a selective barrier acting as a supported liquid membrane (SLM). The SLM nature is a fundamental parameter, and its selection is critical to carry out successful extractions. There are numerous SLMs that have been successfully employed in a wide variety of application fields. The latter is due to the specificity of the selected organic solvents, which allows the extraction of compounds of a very different nature. In the last decade, solid supports and SLM have evolved towards "green" and environmentally friendly materials and solvents. In this review, solid supports implemented in LPME and EME will be discussed and summarized, as well as their applications. Moreover, the advances and modifications of the solid supports and the SLMs to improve the extraction efficiencies, recoveries and enrichment factors are discussed. Hollow fiber and flat membranes, including microfluidic systems, will be considered depending on the technique, configuration, or device used.

On-Chip Electromembrane Surrounded Solid Phase Microextraction for Determination of Tricyclic Antidepressants from Biological Fluids Using Poly(3,4-ethylenedioxythiophene)-Graphene Oxide Nanocomposite as a Fiber Coating

In the present study, on-chip electromembrane surrounded solid phase microextraction (EM-SPME) was employed in the determination of tricyclic antidepressants (TCAs), including amitriptyline, nortriptyline, imipramine, desipramine, maprotiline, and sertraline, from various biological fluids. In this regard, poly(3,4-ethylenedioxythiophene)-graphene oxide (PEDOT-GO) was electrodeposited on an SPME fiber as a conductive coating, then the fiber played the acceptor-electrode role during the extraction. Thus, the immigration of the analytes under the influence of an electric field and their absorption onto the fiber coating were accomplished simultaneously. Under the optimized conditions, the limits of detection for the target analytes were acquired in the range of 0.005-0.025 µg L^-1 using gas chromatography-mass spectrometry. The linearity of the method was 0.010-500 µg L^-1 for the imipramine and sertraline, 0.025-500 µg L^-1 for the amitriptyline, nortriptyline, and desipramine, and 1.000-250 µg L^-1 for the maprotiline (R² ≥ 0.9984). Moreover, this method provided suitable precision and fiber-to-fiber reproducibility, with RSDs ≤ 8.4%. The applicability of the proposed setup was eventually investigated for extraction of the drugs from human bone marrow aspirate, urine, plasma, and well water samples, in which satisfactory relative recoveries, from 93-105%, were obtained.

Carrasco-Correa E, Varanasupakul P, Kubáň P, Miró M. Programmable Millifluidic Platform Integrating Automatic Electromembrane Extraction Cleanup and In-Line Electrochemical Detection: A Proof of Concept

A fully automatic millifluidic sensing platform coupling in-line nonsupported microelectromembrane extraction (μ-EME) with electrochemical detection (ECD) is herein proposed for the first time. Exploiting the features of the second generation of flow analysis, termed sequential injection (SI), the smart integration of SI and μ-EME-ECD enables (i) the repeatable formation of microvolumes of phases for the extraction step in a membrane-less (nonsupported) arrangement, (ii) diverting the acceptor plug to the ECD sensing device, (iii) in-line pH adjustment before the detection step, and (iv) washing of the platform for efficient removal of remnants of wetting film solvent, all entirely unsupervised. The real-life applicability of the miniaturized sensing system is studied for in-line sample cleanup and ECD of diclofenac as a model analyte after μ-EME of urine as a complex biological sample. A comprehensive study of the merits and the limitations of μ-EME solvents on ECD is presented. Under the optimal experimental conditions using 14 μL of unprocessed urine as the donor, 14 μL of 1-nonanol as the organic phase, and 14 μL of 25 mM NaOH as the acceptor in a 2.4 mm ID PTFE tubing, an extraction voltage of 250 V, and an extraction time of 10 min, an absolute (mass) extraction recovery of 48% of diclofenac in urine is obtained. The proposed flow-through system is proven to efficiently remove the interfering effect of predominantly occurring organic species in human urine on ECD with RSD% less than 8.6%.

Nylon Membrane-Based Electromembrane Extraction Coupled with Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry for the Determination of Insulin

A rapid and sensitive protein determination method that uses electromembrane extraction (EME) and is coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) is developed. A flat nylon membrane is used to collect proteins from an aqueous solution and is directly analyzed by MALDI/MS after the addition of the MALDI matrix. Insulin is used as a model protein to investigate the optimum extraction of the parameters. The optimum EME conditions are obtained at 12 V of voltage, 10 min of extraction time, 12 mL sample volume, and 400 rpm agitation rate. The linear dynamic range (LDR) of insulin in an aqueous solution is in the range of 1.0–100.0 nM. The limit of detection (LOD) for insulin in an aqueous solution is 0.3 nM with 103-fold signal-to-noise (S/N) ratio enhancement. Furthermore, the applicability of this method to determine insulin in complicated sample matrices is also investigated. The LDR of insulin in human urine samples is in the range of 5.0–100.0 nM, and the LOD of insulin in urine samples is calculated to be 1.5 nM. The precision and accuracy of this method are evaluated at three different concentration levels, and the coefficient of variation (CV) and relative error are less than 6%. This approach is time-efficient and economical, as the flat membrane mode of EME coupled with MALDI/MS is suitable.

Electromembrane Extraction of Naphthenic Acids in Produced Water Followed by Ultra-High-Resolution Mass Spectrometry Analysis

Naphthenic acids comprise one of the most toxic compounds of the produced water released from offshore oil platforms. Therefore, developing and applying faster, simpler, and more efficient analytical methods for analyzing naphthenic acids are urgently needed. Electromembrane extraction (EME) uses the electrokinetic migration of target ions through a porous membrane. Herein, the EME method was applied to extract naphthenic acids from produced water. The EME method was optimized, and the optimal conditions encompassed decanol as the organic solvent, the sample with pH 10.0, 5 min of extraction at 200 V, and the ratio 4:1 (borate buffer/matrix, v/v). Electrochemical impedance spectroscopy confirmed charged species' migration from produced water through the EME. Subsequently, all extracts were analyzed by ultra-high-resolution mass spectrometry. The EME efficiency was assessed by comparing the extraction results to the liquid-liquid extraction (LLE) method results. Analytical results showed good linearity for both solvent and matrix curves (R² > 0.98). Low detection limits ranged from 0.10 to 0.13 μg mL^-1 and quantification limits from 0.36 to 0.45 μg mL^-1. Precision and accuracy values ranged from -13.3% to 16.5%. These values fit the proposed method, demonstrating that the EME was more efficient than LLE in naphthenic acid extraction. The EME method preferably extracted aromatic compounds with double-bond equivalence from 6 to 8. The EME coupled with ultra-high-resolution mass spectrometry was demonstrated as a promising analytical approach to naphthenic acid extraction as an efficient and more environmentally friendly alternative to conventional extraction methods.

Analysis of methamphetamine, methadone, tramadol, and buprenorphine in biological samples by ion mobility spectrometry after electromembrane extraction in tandem with slug flow microextraction

A novel tandem extraction method based on electromembrane extraction (EME) and slug flow microextraction (SFME) was developed for the extraction of some narcotics (methamphetamine, methadone, tramadol, and buprenorphine) from biological samples. The analytes were quantified by corona discharge-ion mobility spectrometry (CD-IMS). In this method, initially, analytes were extracted using an EME procedure (step-1). After that, the acceptor solution of the first step containing target analytes was applied in an SFME procedure (step-2) as a donor solution for further preconcentration. In the second step, analytes were extracted from an aqueous solution into an organic extractant. The optimum EME and SFME conditions were as follows: type of supported liquid membrane: 2-nitrophenyl octyl ether containing 10% v/v di-(2-ethylhexyl) phosphate, acceptor solution pH: 1.0, sample solution pH: 4.0, voltage: 248 V, extraction time: 17.5 min, tilting number of glass capillary tube: 10 times, type of the organic extractant: toluene, the concentration of NaOH solution: 400 mM. Under optimum extraction conditions, good linearity was obtained in the range of 0.50-750.0 ng/mL with coefficients of determination (r²) ≥ 0.991. The limits of detection and quantification were achieved in the range of 0.15-3.5 ng/mL and 0.50-12.0 ng/mL, respectively. The inter-day and intra-day precisions (n = 3) provided RSDs lower than 12.8% and 12.7%, respectively. Enrichment factors and extraction recoveries of the analytes were in the range of 255.7 to 505.4 and 37.6-78.3%, respectively. Comparing the EME/HPLC-UV with EME-SFME/CD-IMS showed that using the tandem extraction method improved the enrichment factors by more than 2.7 times and limits of detection and quantification by more than 15 times. Finally, this procedure was used to quantify target analytes in plasma and urine samples.

A novel 3D printed device with conductive elements for electromembrane extraction combined with HPLC and UV detector

This paper is focused on proposing for a new design and setup for electromembrane extraction. A new cap was designed and conductive vials of different shape were fabricated using three-dimensional printing. The new cap holds three fibers to enhance electromembrane extraction recovery. Conductive vials can simultaneously perform as electrodes therefore, there is no need to include an electrode in sample solutions. Phenobarbital and phenytoin were used as model compounds to assess the setup performance. Under optimal conditions, these analytes were extracted from the sample solution at pH = 9 to the acceptor solution at pH = 13 with a voltage of 40 V for 20 min, while 1-octanol was employed as the supported-liquid-membrane. The influence of conductive vials geometry on the recovery was examined and effects of different shapes were studied by performing numerical simulation to establish electric potential distribution. Of the vials tested with circular, triangular and floral-like cross-sections the latter exhibited the best voltage distribution. The circular vial had the highest recovery attributed to its better hydrodynamic shape, which allows rapid fluid sample transport and therefore enhanced system recovery. The extraction recovery and RSD of circular vial with three fibers was 33.0 and 7.6 for phenobarbital and 42.2 and 10.4 for phenytoin. This article is protected by copyright. All rights reserved.

Electromembrane Extraction and Dual-Channel Nanoelectrospray Ionization Coupled with a Miniature Mass Spectrometer: Incorporation of a Dicationic Ionic Liquid-Induced Charge Inversion Strategy

Green analytical chemistry aims at developing analytical methods with minimum use and generation of hazardous substances for the protection of human health and the environment. To address this need, a green analytical protocol has been developed for the analysis of anionic compounds integrating electromembrane extraction (EME), dual-channel nanoelectrospray ionization (nanoESI), and a miniature mass spectrometer. Haloacetic acids (HAAs) have attracted considerable public concern due to their adverse effects on human health and were selected as model analytes for method development. A flat membrane EME device was developed and assembled in-house. Optimization of fundamental operational parameters was performed using single-factor test and response surface methodology. Both the EME acceptor phase and an imidazolium-based dicationic ionic liquid (DIL), 1,1-bis(3-methylimidazolium-1-yl) butylene difluoride (C₄(MIM)₂F₂), were subjected to dual-channel nanoESI and miniature mass spectrometry analysis based on a charge inversion strategy, where positively charged complexes were formed. Enhancement in signal intensity by as much as 2 magnitudes was achieved in the positive-ion mode compared to the negative-ion mode in the absence of the dicationic ion-pairing agent. The developed protocol was validated, obtaining good recoveries ranging from 82.7 to 109.9% and satisfactory sensitivity with limits of detection (LODs) and quantitation (LOQs) in the ranges of 1-5 and 2-10 μg/L, respectively. The greenness of the analytical procedure was assessed with a calculated score of 0.71, indicating a high degree of greenness. The developed method was applied to the analysis of real environmental or municipal water samples (n = 16), exhibiting appealing potential for outside-the-laboratory applications.

Electromembrane extraction of polar substances - Status and perspectives

In this article, the scientific literature on electromembrane extraction (EME) of polar substances (log P < 2) is reviewed. EME is an extraction technique based on electrokinetic migration of analyte ions from an aqueous sample, across an organic supported liquid membrane (SLM), and into an aqueous acceptor solution. Because extraction is based on voltage-assisted partitioning, EME is fundamentally suitable for extraction of polar and ionizable substances that are challenging in many other extraction techniques. The article provides an exhaustive overview of papers on EME of polar substances. From this, different strategies to improve the mass transfer of polar substances are reviewed and critically discussed. These strategies include different SLM chemistries, modification of supporting membranes, sorbent additives, aqueous solution chemistry, and voltage/current related strategies. Finally, the future applicability of EME for polar substances is discussed. We expect EME in the coming years to be developed towards both very selective targeted analysis, as well as untargeted analysis of polar substances in biomedical applications such as metabolomics and peptidomics.

Effect of sample matrices on supported liquid membrane: Efficient electromembrane extraction of cathinones from biological samples

In this work, the effect of sample matrix on electromembrane extraction (EME) was investigated for the first time using cathinones (log P < 1.0) as polar basic model analytes. Ten supported liquid membranes (SLMs) were tested for EME from spiked buffer solutions, urine, and whole blood samples, respectively. For buffer solutions, SLMs containing aromatic solvents provided higher EME recovery than non-aromatic solvents, which confirmed the significance of cation-π interactions for EME of basic substances. Interestingly, when applied to urine and whole blood samples, aromatic SLMs were less efficient, while non-aromatic SLMs containing abundant hydrogen-bond acidity/basicity were efficient. These observations were explained by SLM fouling, and the antifouling property of the SLM was clearly dependent on the nature of the SLM solvent. Accordingly, a binary SLM containing aromatic 1-ethyl-2-nitrobenzene (ENB) and non-aromatic 1-undecanol (1:1 v/v) was developed. This binary SLM was not prone to fouling, and provided high recoveries of cathinones from urine and whole blood. EME based on this SLM was optimized and evaluated in combination with liquid chromatography tandem mass spectrometry (LC-MS/MS), and the linear ranges with R² ≥ 0.9903 for cathinones in whole blood and urine were 5-200 ng/mL and 1-200 ng/mL, respectively. The LOD and LOQ of cathinones were ranged from 0.12 to 0.54 ng/mL and 0.38-1.78 ng/mL, respectively. The repeatability and accuracy bias at three levels were ≤11% and within 10%, respectively. In addition, the matrix effect ranged from 88% to 118% was also in compliance with guidelines for bioanalytical method validation provided by the European Medicines Agency.

Recent sample pretreatment methods for determination of selective serotonin reuptake inhibitors (SSRIs) in biological samples

Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (FLU), sertraline (SER), paroxetine (PAR), fluvoxamine (FLV) and citalopram (CIT) have been the first treatment drugs for pregnant and breastfeeding women. Quantitative analysis of SSRIs in biological samples is extremely needed in public health and clinical practice. During the analysis, sample pretreatment is an important step that can obtain an accurate quantitative analysis of SSRIs in the complex samples. The present paper discussed the recent development of sample preparation methods for SSRI analysis. Traditional sample preparation techniques such as liquid liquid extraction (LLE) and solid phase extraction (SPE), which have been widely used in the separation of SSRIs in biological samples, were extensively presented. Moreover, the new sample preparation techniques including liquid phase microextraction (LPME), solid phase microextraction (SPME), electromembrane extraction (EME) and other miniaturized extraction techniques, which are becoming highly popular in SSRI analysis, were also critically reviewed. In this review, both the advantages and disadvantages of these sample pretreatment methods were addressed. As a summary, we prospected the challenges and promising directions for the future of sample pretreatment methods in SSRI analysis.

Application of Capillary Electrophoresis for Determination of Inorganic Analytes in Waters

Aside from HPLC and GC, capillary electrophoresis (CE) is one of the most important techniques for high-performance separations in modern analytical chemistry. Its main advantages are the possibility of using different detection techniques, the possibility of in-capillary sample processing for preconcentration or derivatization, and ease of instrumental miniaturization down to the microfluidic scale. Those features are utilized in the separation of macromolecules in biochemistry and in genetic investigations, but they can be also used in determinations of inorganic ions in water analysis. This review, based on about 100 original research works, presents applications of CE methods in water analysis reported in recent decade, mostly regarding conductivity detection or indirect UV detection. The developed applications include analysis of high salinity sea waters, as well as analysis of other surface waters and drinking waters.

Ultrasound-assisted electromembrane extraction with supported semi-liquid membrane

Electromembrane extraction (EME), involving the migration of charged analytes across a supported liquid membrane (SLM) with an external power supply, is a promising sample preparation method in analytical chemistry. However, the presence of boundary double layers at the SLM/solution interfaces often restricts extraction efficiency. To avoid this, the current work proposed an ultrasound-assisted EME (UA-EME) method based on a novel type of supported semi-liquid membrane (SsLM). The characterizations showed that the SsLM was stable under ultrasound conditions. Ultrasound was found to reduce the boundary double layers and thus increase the mass transfer. Major operational parameters in UA-EME including ultrasound power density, temperature, applied voltage and extraction time were optimized with haloperidol, fluoxetine, and sertraline as model analytes. Under the optimal conditions, extraction recoveries of model analytes in water samples were in the range of 66.8%-91.6%. When this UA-EME method was coupled with LC-MS/MS for detection of the target analytes in human urine samples, the linear range of the analytical method was 10-1000 ng mL^-1, with R² > 0.997 for all analytes. The limits of detection (LOD) and limits of quantification (LOQ) were in the range of 1.7-2.1 ng mL^-1 and 5.7-6.7 ng mL^-1, respectively. The UA-EME expands the application field of ultrasound chemistry and will be very important in development of stable and fast sample preparation systems in the future.

Electromembrane extraction in microfluidic formats

Electromembrane extraction is a microextraction technique where charged analytes are extracted across a supported liquid membrane and selectively isolated from the sample based on an electrical field. Since the introduction in 2006, there has been continuously increasing interest in electromembrane extraction, and currently close to 50 new articles are published per year. Electromembrane extraction can be performed in different technical configurations, based on standard laboratory glass vials or 96-well plate systems, and applications are typically related to pharmaceutical, environmental, and food and beverages analysis. In addition to this, conceptual research has developed electromembrane extraction into different milli- and microfluidic formats. These are much more early-stage activities, but applications among others related to organ-on-chip systems and smartphone detection indicate unique perspectives. To stimulate more research in this direction, the current article reviews the scientific literature on electromembrane extraction in milli- and microfluidic formats. About 20 original research articles have been published on this subject so far, and these are discussed critically in the following. Based on this and the authors own experiences with the topic, we discuss perspectives, challenges, and future research.

Chitosan biofilms: Insights for the selective electromembrane extraction of fluoroquinolones from biological samples

A selective electromembrane extraction procedure for the extraction of Enrofloxacin, Marbofloxacin and Flumequine, usually employed as antibiotic in veterinarian use, is proposed by using a chitosan biofilm, composed by 60% (w/w) chitosan and 40% (w/w) Aliquat®336, as active biopolymeric support. The interaction mechanism occurring between the target drugs and the biopolymer has been deeply studied using the Quantum Theory of Atoms in Molecules. The obtained results show the interaction between the extracted fluoroquinolones and the biomembrane is stabilized by two hydrogen bonds formed between both the carboxyl and keto groups of the drugs with both the amine and hydroxyl groups of glucosamine in the biopolymer. The energetic results agree with the high extraction efficiency obtained for Marbofloxacin, Enrofloxacin and Flumequine in terms of enrichment factors (83, 82 and 58, respectively) in presence of other fluoroquinolones. Under optimum conditions, the proposed electromembrane extraction method exhibits wide linear ranges of 4.2-200 μg L^-1, 5.6-200 μg L^-1 and 5.1-200 μg L^-1, respectively; low limits of detection close to 1.3 μg L^-1 and appropriate repeatability (relative standard deviation values 4-7%).

Removal of Polymerase Chain Reaction Inhibitors by Electromembrane Extraction

Polymerase chain reaction (PCR) technology has become the cornerstone of DNA analysis. However, special samples (e.g., forensic samples, soil, food, and mineral medicine) may contain powerful PCR inhibitors. High levels of inhibitors can hardly be sufficiently removed by conventional DNA extraction approaches and may result in the complete failure of PCR. In this work, the removal of PCR inhibitors by electromembrane extraction (EME) was investigated for the first time. To demonstrate the universality of the approach, EME formats with and without supported membranes (termed parallel-EME and μ-EME, respectively) were employed, and both anionic [humic acid (HA)] and cationic (Ca²⁺) PCR inhibitors were used as models. During EME, charged inhibitors in the sample migrate into the liquid membrane in the presence of an electric field and might further leech into the waste solution, while PCR analytes remain in the sample. After EME, the clearance values for HA at 0.2 and 2.5 mg mL^-1 were 94 and 85%, respectively, and that for Ca²⁺ (275 mM) was 63%. Forensic PCR-short tandem repeat (PCR-STR) genotyping showed that EME significantly reduced the interference by HA in PCR-STR analysis and displayed a higher HA purge capability compared to existing methods. Furthermore, by combining EME with liquid-liquid extraction or solid-phase extraction, satisfactory STR profiles were obtained from HA-rich blood samples. In addition, false-negative reports of bacterial detection in mineral medicine and shrimps were avoided after the removal of Ca²⁺ by μ-EME. Our research demonstrates the great potential of EME for the purification of DNA samples containing high-level PCR inhibitors and opens up a new application direction for EME.

Molecularly imprinted polypyrrole@CuO nanocomposite as an in-tube solid-phase microextraction coating for selective extraction of carbamazepine from biological samples

A nanocomposite of molecularly imprinted polypyrrole on copper oxide (MIP@CuO) was introduced as a new coating for in-tube solid-phase microextraction (IT-SPME). The method coupled with HPLC-UV was successfully applied for analysis of carbamazepine (anticonvulsant and bipolar disorder medication) in biological samples. First, in order to increase the surface area and stability of the coating, copper oxide (CuO) nanosheets were synthesized on the inner surface of a copper tube using a chemical method. Then, molecularly imprinted polypyrrole coating (using carbamazepine as a template) was deposited on CuO by a facile in-situ electrodeposition method. According to the results, The MIP@CuO coating shows long life time, enhanced extraction efficiency, and good clean-up, for pre-concentration and determination of carbamazepine in biological samples. The synthesized adsorbent also showed high selectivity to carbamazepine compared to other drugs with similar structure. Important factors affecting the extraction efficiency of the analyte in the in-tube SPME method, such as salt concentration, extraction and desorption times, flowrates of the sample solution, and eluent, were optimized. Under optimal conditions, the method showed good linearity for carbamazepine in the range of 0.05-500 μg L^-1, 0.10-500 μg L^-1, and 0.10-500 μg L^-1 in water, urine, and plasma samples, respectively, with coefficients of determination better than 0.996. The limits of detection were in the range of 0.01-0.05 μg L^-1 in different matrices. The intra- and inter-assay precisions (RSD%, n = 3) were in the range of 6.7-8.1 % and 7.1-9.5 %, respectively.

Application of reusable flat-membrane in electro-membrane extraction for tamsulosin hydrochloride determination in cleaning validation samples of sterile production line equipment by RP-HPLC

In order to ensure compliance with the current Good Manufacturing Practice (cGMP), cleaning process of pharmaceutical manufacturers should be validated. This study was aimed to utilize a reusable flat-membrane in the electromembrane extraction (EME) for isolation of tamsulosin hydrochloride (TMS) from rinse samples of sterile production of pharmaceutical line. Moreover, validation of mentioned method was done. The residual concentration of TMS was determined by RP-HPLC. Effective parameters such as pH, applying voltage and extraction time were optimized individually. Optimum conditions were found 12, 100 V and 10 min for pH, applying voltage and extraction time, respectively. Figures of merit were calculated under optimum conditions, therefore, linear range and limit of detection (LOD) were obtained 0.5-1000 ng mL^-1 with a good coefficient of determination (R²=0.9901) and 0.05 ng mL^-1, respectively. Last but not least, RSD of determination was found 0.67% which shows a satisfactory repeatability. According to the obtained results, proposed method is a precise, accurate, relatively fast and applicable route to determine TMS concentrations in rinse samples.

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.

Direct coupling of paper spray mass spectrometry and four-phase electroextraction sample preparation

This paper presents a novel coupling between a four-phase electroextraction (EE) system and paper spray mass spectrometry (PS-MS) for the extraction, pre-concentration, and direct analysis of target compounds in different samples. The approach, EE-PS-MS, is based on the sorption of analytes directly on the tip of a triangular-shaped chromatographic paper, with subsequent prompt analysis by PS-MS. Thus, no off-line extraction step is required before the PS analysis, improving the protocol efficiency and reducing the analysis time. In addition to functioning as a porous material to absorb the target compounds, the chromatographic paper also served as the support for one of the aqueous phases of the optimized four-phase electroextraction system. Extraction conditions, such as the composition of the donor and organic phases, applied electric potential, and extraction time, were optimized. Three different applications, involving biofluid, food, and water quality analysis, were evaluated as a proof-of-concept. These applications involved the determination of (i) cocaine and lidocaine in saliva, (ii) malachite green in tap water, and (iii) bisphenol A (BPA) in red wine. When compared with direct PS-MS, the novel EE-PS-MS protocol improved the sensitivities by factors ranging from 14 to 110, depending on the analyte and the sample. The electroextraction procedures were performed on a laboratory-built 66-well plate, which offered the functionality of simultaneous sample handling and, most importantly, improved analytical throughput.

Large-volume electric field-assisted multiphase extraction of malachite green from water samples: A multisample device and method validation

In this work, a new large-volume multiphase, multi-sample electroextraction device was developed and applied to selectively extract malachite green (MG) from water samples. This device was easily constructed with ordinary materials and capable of extracting ten samples simultaneously, obtaining MG preconcentrated on a solid support, to fit into a pipette tip. A multi-well plate was applied to extract MG from aquaculture water samples, and the extracts containing the desorbed MG were analysed by LC-DAD and LC-MS/MS. The signals from both detectors were used in two independent validation procedures. Linearity, matrix effect, selectivity, precision, trueness, and limits of detection and quantification were all evaluated. For both detectors, linearity was demonstrated in the range of 0.5-5 μg L^-1 (R² > 0.98). Matrix effect was insignificant for LC-DAD only, and the average preconcentration factor was about 60 times. Recoveries ranged from 94 to 113% for LC-DAD and 95-115% for LC-MS/MS analysis. ANOVA was applied to estimate the standard deviation under repeatability (6.96-8.61% for LC-DAD and 5.98-7.41% for LC-MS/MS) and within-reproducibility (6.96-8.61% for LC-DAD and 6.56-7.41% for LC-MS/MS) conditions. The limits of detection and quantification for LC-MS/MS analysis were 4.29 and 28.74 ng L^-1, respectively, while, for LC-DAD, these limits were 14.29 and 95.81 ng L^-1, respectively. The results demonstrated that the developed method was suitable for determining MG in water samples, and the large-volume multiphase, multi-sample electroextraction device proved to be a powerful sample preparation technique to obtain high clean-up and large preconcentration levels, which are of paramount importance for environmental applications.

Two-phase agarose gel-electromembrane extraction: Effect of organic solvent as an acceptor phase in electroendosmosis flow phenomenon

In this study, a new mode of gel electromembrane extraction (G-EME) namely as "Two-phase G-EME", is suggested for the sensitive quantification of five basic drugs (desipramine, clomipramine, trimipramine, citalopram and clozapine) in biological samples. Compared to classical G-EME which is based on aqueous-gel-aqueous layout, herein, the aqueous acceptor phase (AP) was replaced with organic solvent. Briefly, negative electrode was immersed into the organic AP (with low conductivity) and positive electrode into the aqueous donor phase (DP). Based on our results, this simple adjustment significantly reduced electroendosmosis (EEO) flow phenomenon which is considered as the main issue in G-EME. In the workflow, target analytes were extracted from the 7.0 mL sample, across the fabricated agarose gel membrane, to the 100 μL of the AP under the optimized extraction conditions (organic solvent type: acetonitrile; pH of gel membrane: 5.0, pH of sample solution: 4.0, voltage: 45 V and extraction time: 22 min). Then, the organic AP with analytes was analyzed by gas chromatography (GC) instrument with flame-ionization detector (FID). The methodology offered limits of detection (LODs) and recoveries in the range of 1.0-1.5 ng mL^-1 and 48.5-89.0 %, respectively. Finally, we note that two-phase G-EME assembly was able to extract analytes-of-interest in the convenient and safe manner from the hazardous and difficult-to-process biological specimens such as human serum and urine.

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.

Electromembrane extraction based on agarose gel for the extraction of phenolic acids from fruit juices

Extraction of polar acidic compounds is a challenging task in electromembrane extraction. In this study, gel-electromembrane extraction was employed for the extraction of phenolic acids as the polar acidic compounds from fruit juices. For this aim, the extraction of phenolic acids from the juice samples (4 mL, pH = 6.0) was carried out across the agarose gel membrane (concentration of agarose; 3% (w/v), pH of gel; 10.0, and thickness of membrane: 3 mm) into the acceptor solution (100 μL, pH = 12.0). Also, this extraction process was conducted by applying the optimum potential (25 V) for 15 min to the extraction system. Under the optimized condition, acceptable linearity (R² ≥ 0.993) over a concentration range of 10.0-2500 ng mL^-1 was achieved. The limits of detection were between 3.0 and 15.2 ng mL^-1, while the corresponding repeatabilities ranged from 5.3 to 11.4% (n = 4). The recoveries achieved for the extraction of target compounds were ranged from 26.8 to 74.4%. The proposed method was used for the extraction of phenolic acids from orange, apple and kiwi juices, and the obtained relative recoveries in the range of 78.0-104.2% and RSDs in the range of 6.3 to 11.3% indicated successful extraction of phenolic acids.

Psychoactive substances in human breast milk: a review of analytical strategies for their investigation

WHO recommends breastfeeding for the first 6 months of newborn's life. Due to its physicochemical properties, breast milk may contain undesirable components originated from mother's feeding, medication and illicit drugs consumption. Some of these substances transferred from bloodstream to milk and delivered to the infant can cause harmful effects. For the last decades, analytical advances enabled the analysis of several substances in milk using different techniques. Thereby, it is possible to evaluate infant's level of exposure to these substances. This review presents the information published in the main scientific dissemination media about psychoactive drugs investigation in human breast milk, involving the sample preparation techniques and chromatographic validated methods developed in the past 10 years.