Aqueous Acceptor Solution Research Articles

Electromembrane Extraction of Ofloxacin from Human Plasma and Its Quantification by Capillary Electrophoresis

Background: Application of electromembrane extraction coupled with capillary electrophoresis was studied for ofloxacin extraction from plasma samples. Methods: Ofloxacin migrated from acidic plasma samples through a thin layer of 1-octanol immobilized in the pores of a porous hollow fiber wall into a 10 µL acidic aqueous acceptor solution located inside the lumen of the fiber. Results: Under optimum conditions influencing electromigration (i.e., 20 min of the operation time, stirring speed of 750 rpm, donor phase pH at 4.0, acceptor pH at 3.0, and applied voltage of 30 V across the supported liquid membrane), ofloxacin was extracted from plasma samples with an enrichment factor of 100-fold corresponding to extraction percent of 24%. The calibration curve showed acceptable linearity in the range of 0.2-7.0 µg.mL-1 (R=0.9993). The limits of detection and quantification of 0.05 and 0.2 µg.mL-1 were obtained, respectively. The inter- and intra-day precision and accuracy were obtained below 8.65%. Conclusion: The validated method was successfully processed for the ofloxacin determination in the plasma samples of patients under ofloxacin therapy. There were no interfering peaks which indicates the great selectivity of the developed method.

High-throughput quantification of emerging ''nitazene'' benzimidazole opioid analogs by microextraction and UHPLC-MS/MS.

Benzimidazole opioids, often referred to as nitazenes, represent a subgroup of new psychoactive substances with a recent increase in fatal overdoses in the US and Europe. With a variety of analogs emerging on the illicit drug market, forensic labs are challenged to identify these potent drugs. We here present a simple quantitative approach for the determination of nine nitazene analogs, namely, clonitazene, etodesnitazene, etonitazene, etonitazepyne, flunitazene, isotonitazene, metodesnitazene, metonitazene, and protonitazene in whole blood using liquid-phase microextraction and electromembrane extraction in a 96-well format and liquid chromatography tandem mass spectrometry. Green and efficient sample preparation was accomplished by liquid-phase microextraction in a 96-well format and resulted in high extraction yields for all analytes (> 81%). Here, blood diluted with buffer (1:1, %v) was extracted from a donor compartment across a thin organic liquid membrane and into an aqueous acceptor solution. The acceptor solution was collected and directly injected into the analysis platform. Chromatographic separation was accomplished with a biphenyl column, allowing for baseline separation of the structural isomers isotonitazene and protonitazene before detection by multiple reaction monitoring. The validation was performed according to Scientific Working Group of Forensic Toxicology guidelines. The calibration range was from 0.5 to 50 nM (except for protonitazene and clonitazene from 0.1 nM) with good linearity and limits of detection down to 0.01 nM. An AGREEprep assessment was performed to evaluate sample preparation greenness, with a final score of 0.71. Nitazenes represent a current threat to public health, and analytical methods that cover a wide range of these analogs are limited. The here described method may assist in the detection of nitazenes in whole blood and prevent these substances from being missed in post-mortem investigations.

Electromembrane extraction of peptides based on hydrogen bond interactions

BackgroundElectromembrane extraction (EME) of peptides reported in the scientific literature involve transfer of net positively charged peptides from an aqueous sample, through a liquid membrane, and into an aqueous acceptor solution, under the influence of an electrical field. The liquid membrane comprises an organic solvent, containing an ionic carrier. The purpose of the ionic carrier is to facilitate peptide solvation in the organic solvent based on ionic interactions. Unfortunately, ionic carriers increase the conductivity of the liquid membrane; the current in the system increases, the electrolysis in sample and acceptor is accelerated, and the extraction system tend to be unstable and suffers from drifting pH. ResultsIn the present work, a broad selection of organic solvents were tested as pure liquid membrane for EME of peptides, without ionic carrier. Several phosphates provided high mass transfer, and tri(pentyl) phosphate was selected since this solvent also provided high operational stability. Among 16 different peptides used as model analytes, tri(pentyl) phosphate extracted those with net charge +1 and with no more than two polar side chains. Tri(pentyl) phosphate served as a very strong hydrogen bond acceptor, while the protonated peptides were hydrogen bond donors. By such, hydrogen bonding served as the primary interactions responsible for mass transfer. Tri(pentyl) phosphate as liquid membrane, could exhaustively extract leu-enkephalin, met-enkephalin, and endomorphin from human blood plasma and detected by LC-MS/MS. Calibration curves were linear (r2 > 0.99) within a concentration range from 1 to 500 ng/mL, and a relative standard deviation within 12% was observed for precision studies. SignificanceThe current experiments are important because they indicate that small peptides of low polarity may be extracted selectively in EME based on hydrogen bond interactions, in systems not suffering from electrolysis.

Micro-electromembrane extraction through volatile free liquid membrane for the determination of β-lactam antibiotics in biological and environmental samples

Micro-electromembrane extraction (μ-EME) was presented for the selective extraction of four main β-lactam antibiotics (penicillin, phenoxypenicillin, ampicillin, and amoxicillin) from complex samples. A volatile solvent (ethyl acetate or chloroform) was sandwiched between a plug of the complex sample and another plug of an aqueous acceptor solution in a transparent polymeric tube and formed the so-called free liquid membrane (FLM). The use of the FLM eliminated the evaporation of the solvent and enabled the μ-EME of the antibiotics, which was carried out by the application of DC voltage to the terminal aqueous solutions. The drugs in the complex sample were selectively transferred through the FLM to the acceptor solution, which was directly used for their determination by micellar electrokinetic chromatography with ultraviolet detection (MEKC-UV). The μ-EME was characterized by sub-μA electric currents, high elimination of matrix components, high stability of operational solutions, and suitability for extracting undiluted complex samples. The μ-EME/MEKC-UV method yielded good analytical repeatability (RSDs of peak areas ≤5%), extraction recoveries (40–84%), accuracy (92–105%) and linearity over one and a half order of magnitude (R2 ≥ 0.9998), and was applied to the determination of the four β-lactam antibiotics in human serum and waste water at clinically and environmentally relevant concentration levels. Further improvement in the method sensitivity was achieved by changing the μ-EME tube geometry (conical shape) and increasing the complex sample volume (100 μL). The analytes were enriched by factors of 7.6–11.5, the limits of detection dropped down to less than 18 ng/mL, and the modified μ-EME/MEKC-UV method enabled the trace determination of β-lactam antibiotics in complex samples.

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.

Impact of ion balance in electromembrane extraction

Electromembrane extraction (EME) involves transfer of analyte ions from aqueous sample, through a supported liquid membrane (SLM), and into an aqueous acceptor solution under the influence of an external electrical field. In addition to target analyte ions, the sample also contains matrix ions, and both the sample and acceptor contains background buffer ions to control pH. The ratio between the total amount of ions in sample and acceptor defines the ion balance (χ). Previous publications have discussed the impact of ion balance, but conclusions are contradictory. Therefore, the current paper investigated the ion balance in more detail. From a theoretical point of view, low χ-values favor EME; buffer anions at high concentration in the acceptor migrate into the SLM, while target cations enters the SLM from the sample to maintain electroneutrality. A large number of experiments was performed in this paper to investigate the practical impact of ion balance. Twelve basic drugs were used as model analytes (0.0 < log P < 5.0), and 2-nitrophenyl octyl ether (NPOE) and NPOE + 5% di(2-ethylhexyl) phosphate (DEHP) were used as SLM. With formate buffer pH 3.75 as sample and acceptor, the impact of χ in the range 0.01–10 was studied without bias from differences in pH. Here model analytes were unaffected by ion balance. Buffers containing propionic, butyric, and valeric acid were also tested. These buffer ions migrated more into the SLM, and affected recoveries in several cases. However, this was due to ion pairing rather than effects of ion balance. Similar behaviors from sodium chloride and urine samples were observed with different χ-values. Thus, in the systems tested, almost no impact of ion balance was found, and this was attributed to very low partition of background buffer and matrix ions into the SLM. On the other hand, extractions were in several cases influenced by ion pairing phenomena.

Combination of gel-electromembrane extraction with switchable hydrophilicity solvent-based homogeneous liquid-liquid microextraction followed by gas chromatography for the extraction and determination of antidepressants in human serum, breast milk and wastewater

The current study presents for the first time a combination of the gel electromembrane extraction (GEL-EME) and switchable hydrophilicity solvent-based homogeneous liquid-liquid microextraction (SHS-HLLME) methods which can be used as an efficient hyphenated extraction procedure. This coupled method, which was followed by GC-FID, was applied for quantification of antidepressants (desipramine, clozapine, and citalopram) in biological and wastewater samples. The effective parameters of both GEL-EME and SHS-HLLME procedures were optimized. Using an agarose gel membrane, analytes were extracted from 7.0 mL of the sample solution to 500 µL of the aqueous acceptor solution. The maximum extraction of analytes of interest was obtained under the optimized conditions (pH of acceptor solution, 5.0; pH of gel membrane, 5.0; pH of sample solution, 7.0, voltage value, 30 V; and extraction time, 30 min). Then, the acceptor solution was transferred to the extraction cell and the SHS-HLLME procedure was conducted again under the optimized conditions. Dipropylamine (50 µL) was selected as an extraction solvent. The introduced technique exhibited good linearities with coefficients of determinatin (R2) higher than 0.983 and an acceptable linear range of 5.0–1000 ng/mL. Accordingly, the limit of detection was ≤ 1.0 ng/mL (S/N = 3) for all analytes, and the high enrichment factors were obtained in the range of 178.7–194.8. Moreover, the corresponding repeatability was from 4.0 to 8.7% (n = 3). The proposed method was successfully utilized to determine trace levels of the drugs in human serum, wastewater, and breast milk samples.

Determination of phenytoin in exhaled breath condensate using electromembrane extraction followed by capillary electrophoresis

Application of hollow fiber-based electromembrane extraction was studied for extraction and quantification of phenytoin from exhaled breath condensate (EBC). Phenytoin is extracted from EBC through a supported liquid membrane consisting of 1-octanol impregnated in the walls of a hollow fiber, and into an alkaline aqueous acceptor solution inside the lumen of the fiber. Under the obtained conditions of electromembrane extraction, that is, the extraction time of 15 min, stirring speed of 750 rpm, donor phase pH at 11.0, acceptor pH at 13.0, and an applied voltage of 15 V across the supported liquid membrane, an enrichment factor of 102-fold correspond to extraction percent of 25.5% was achieved. Good linearity was obtained over the concentration range of 0.001-0.10 µg/mL (r2 = 0.9992). Limits of detection and quantitation were 0.001 and 0.003 µg/mL, respectively. The proposed method was successfully applied to determine phenytoin from EBC samples of patients receiving the drug. No interfering peaks were detected that indicating excellent selectivity of the method. The intra- and interday precisions (RSDs) were less than 14%.

Tandem dispersive liquid–liquid microextraction coupled with micro-sampling flame atomic absorption spectrometry for rapid determination of lead(II) and cadmium(II) ions in environmental water samples

ABSTRACT Tandem dispersive liquid liquid microextraction coupled with micro - sampling flame atomic absorption spectrometry for rapid determination of lead2 and cadmium2 ions in environmental water samples. A simple method termed as tandem dispersive liquid–liquid microextraction coupled with micro-sampling flame atomic absorption spectrometry is used for determination of the lead(II) and cadmium(II) ions in different environmental water samples. According to the proposed method, the target analytes are extracted from an aqueous sample solution (10 mL) into a micro-volume of an organic solvent, and then they are selectively back-extracted into an aqueous acceptor solution (150 μL) to increase the compatibility of the extractant phase with a final analyser system and provide a suitable enrichment factor. The developed method is very fast, implemented in just about 7 min, and provides a high sample clean-up. The factors influencing the extraction efficiency including the type and volume of the organic solvent, pH and volume of the acceptor solution, and number of extractions are thoroughly examined and optimised. Under the optimal experimental conditions, the developed method provides a good linearity (in the range of 0.4–300 ng mL−1 (R2 ≥ 0.994)), and low limits of detection (in the range of 0.07–0.31 ng mL−1). Finally, the method is successfully applied for the direct determination of the understudied analytes in the river, dam, and well water samples.

Electromembrane extraction-looking into the future.

Analytical microextraction techniques, including solid-phase microextraction (SPME) Arthur & Pawliszyn (Anal Chem 62:2145-2148, 1990), stir bar sorptive extraction (SBSE), Baltussen et al. (J Microcol 11:737-747, 1999), single-drop microextraction (SDME) Jeannot & Cantwell (Anal Chem 68:2236-2240, 1996), hollow-fiber liquid-phase microextraction (HF-LPME) Pedersen-Bjergaard & Rasmussen (Anal Chem 71:2650-2656, 1999), dispersive liquid-liquid microextraction (DLLME) Berijani et al (J Chromatogr A. 1123:1-9, 2006), and electromembrane extraction (EME) Pedersen-Bjergaard & Rasmussen (J Chromatogr A 1109:183-190, 2006) have gained considerable interest in recent years. The latter technique, EME, differs from the others by the fact that mass transfer and extraction is facilitated by electrokinetic migration. Thus, basic or acidic analytes are extracted in their ionized form from aqueous sample, through an organic supported liquid membrane (SLM) and into an aqueous acceptor solution under the influence of an electrical potential. EME provides pre-concentration and sample clean-up, and can be performed in 96-well format using only a few microliter organic solvent per sample (green chemistry). Extraction selectivity is controlled by the direction and magnitude of the electrical field, by the chemical composition of the SLM, and by pH in the acceptor solution and sample. This trends article discusses briefly the principle, performance, and current status of EME, and from this future directions and perspectives are identified. Unlike traditional extraction methods, EME involves electrokinetic transfer of charged analyte molecules across an organic phase (SLM) immiscible with water. This process is still not fully characterized from a fundamental point of view, and more research in this area is expected in the near future. From author's point of view, such research at the interface between electrophoresis and partition will be highly important for future implementation of EME. Graphical abstract ᅟ.

Selective determination of chromium(VI) ions using in-tube electro-membrane extraction followed by flame atomic absorption spectrometry

In the present work, a novel and efficient method, namely in-tube electro-membrane extraction followed by flame atomic absorption spectrometry (IEME-FAAS), is used for the selective determination of chromium(VI) ions in some environmental samples. In this approach, which is based upon the electro-kinetic migration of ionized compounds, by applying an electrical potential difference, the analyte is extracted from an aqueous sample solution through a supported liquid membrane (SLM) into an acceptor solution. A thin polypropylene (PP) sheet placed inside a tube acts as a support for the membrane solvent used, and 100μL of an aqueous acceptor solution is separated by this solvent from 5.0mL of an aqueous donor solution. In order to achieve the best extraction efficiency, the effective parameters involved including the voltage magnitude, SLM solvent, extraction time, and pH range are optimized. Under the optimized experimental conditions, the IEME-FAAS method provides a good linearity in the range of 10.0–600ngmL−1, a low limit of detection (3.0ngmL−1), and good extraction repeatabilities (RSDs below 8.6%, n=5). Finally, the developed method is used for the selective determination of chromium(VI) ions in the tap, river, and mineral water samples.

Parallel artificial liquid membrane extraction of new psychoactive substances in plasma and whole blood.

Parallel artificial liquid membrane extraction (PALME) was combined with ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) and the potential for screening of new psychoactive substances (NPS) was investigated for the first time. PALME was performed in 96-well format comprising a donor plate, a supported liquid membrane (SLM), and an acceptor plate. Uncharged NPS were extracted from plasma or whole blood, across an organic SLM, and into an aqueous acceptor solution, facilitated by a pH gradient. MDAI (5,6-methylenedioxy-2-aminoindane), methylone, PFA (para-fluoroamphetamine), mCPP (meta-chlorophenylpiperazine), pentedrone, methoxetamine, MDPV (methylenedioxypyrovalerone), ethylphenidate, 2C-E (2,5-dimethoxy-4-ethylphenethylamine), bromo-dragonfly, and AH-7921 (3,4-dichloro-N-{[1-(dimethylamino)cyclohexyl]methyl}benzamide) were selected as representative NPS. Optimization of operational parameters was necessary as the NPS were novel to PALME, and because PALME was performed from whole blood for the very first time. In the PALME method developed for plasma, NPS were extracted from a 250μL alkalized donor solution consisting of 125μL plasma sample, 115μL 40mM NaOH, and 10μL internal standard. In the PALME method from whole blood, the 250μL alkalized donor solution consisted of 100μL whole blood, 50μL deionized water, 75μL 80mM NaOH, and 25μL internal standard. In both methods, extraction was accomplished across an SLM of 5μL dodecyl acetate with 1% trioctylamine (w/w), and further into an acidic acceptor solution of 50μL 20mM formic acid. The extraction was promoted by agitation at 900rpm and was carried out for 120min. Method validation was performed and the following parameters were considered: linearity, limits of quantification (LOQ), intra- and inter-day precision, accuracy, extraction recoveries, carry-over, and matrix effects. The validation results were in accordance with FDA guidelines.

Micro-electromembrane extraction using multiple free liquid membranes and acceptor solutions – Towards selective extractions of analytes based on their acid-base strength

This work investigated selective micro-electromembrane extractions (μ-EMEs) of the colored indicators metanil yellow and congo red (visual proof-of-principle) and the small drug substances nortriptyline, papaverine, mianserin, and citalopram (model analytes) based on their acid-base strength. With two free liquid membranes (FLMs), the target analytes were extracted from aqueous donor solution, across FLM 1 (1-pentanol, 1-ethyl-2-nitrobenzene (ENB) or 4-nitrocumene (4-NC)), into aqueous acceptor solution 1, further across FLM 2 (1-pentanol, ENB or 4-NC), and finally into aqueous acceptor solution 2. All phases had volumes between 1.0 and 1.5 μL and extractions were promoted by 200–300 V d.c. applied across the five-phase μ-EME system formed in a perfluoroalkoxy capillary tubing. The anode was located in acceptor solution 2 and the cathode was located in donor solution for μ-EMEs of acidic analytes, and locations of the electrodes were vice versa for μ-EMEs of basic analytes. After μ-EME, donor solution and acceptor solution 1 and 2 were analyzed by capillary electrophoresis or liquid chromatography-mass spectrometry. The model analytes migrated efficiently in the proposed μ-EME system, their migration behavior was controlled by pH in aqueous solutions and their selective fractionation into acceptor solution 1 and 2 was demonstrated based on their acid-base strength. Under optimal conditions, acceptor solution 2 contained 60% nortriptyline (pKa = 10.5) and less than 1% papaverine (pKa = 6.0) and acceptor solution 1 contained 17% nortriptyline and 27% papaverine after 15 min of μ-EME. The five-phase μ-EME system was also compatible with human plasma samples. Work is in progress to further increase the fractionation capability, and to implement the concept into microfluidic platforms.

Introduction of high nitrogen doped graphene as a new cationic carrier in electromembrane extraction.

This paper proposes for the first time, the use of high nitrogen doped graphene (HND-G) as a new cationic carrier for the enhancement of electromembrane extraction (EME) performance. Sensitivity of EME was improved by the modification of supported liquid membrane composition through the addition of HND-G into 1-octanol for the extraction of naproxen and sodium diclofenac as model acidic drugs. The comparison between HND-G-modified EME and conventional EME showed that HND-G could increase the overall partition coefficient of acidic drugs in the membrane due to the fact that HND-G acts as an ion pair reagent and there is an electrostatic interaction between positively charged HND-G and acidic drugs with negative charge. During the extraction, model acidic drugs migrated from a 10 mL aqueous sample solution (pH 9.6) through a thin layer of 1-octanol containing 0.6% w/v of HND-G that was impregnated in the pores of a hollow fiber, into a 30 μL basic aqueous acceptor solution (pH 12.3) present in the lumen of the hollow fiber. Equilibrium extraction conditions were obtained after 16 min of operation with the whole assembly agitated at 1000 rpm. Under the optimized conditions, the enrichment factors were between 238 and 322 and also the LODs ranged from 0.1 to 0.7 ng/mL in different samples. Finally, the applicability of this method was evaluated by the extraction and determination of drugs of interest in real urine samples.

Electromembrane extraction coupled to square wave anodic stripping voltammetry for selective preconcentration and determination of trace levels of As(III) in water samples

In this Study for the first time, a combination of electromembrane extraction (EME) and anodic stripping voltammetry (ASV) using a gold nanoparticle-modified glassy carbon electrode (AuNPs/GCE) is introduced, for selective and sensitive determination of trace As(III) in water samples. The process was based on the electrokinetic migration of As(III) ions from a donor phase (sample solution) toward an electrode with opposite charge and into an alkaline aqueous acceptor solution placed inside the lumen of a hollow fiber. The acceptor solution was then analyzed using anodic stripping voltammetry. A linear relationship was observed between the ASV peak currents and the concentration of As(III) ions over two intervals in the range of 0.5–10μg/L and 10–600μg/L. The detection limit of the proposed method was found to be 0.18μg/L using three sigma criteria and the relative standard deviations for 5 replicate measurements of three different concentration levels of As(III) were found to be within the range of 6.7–8.5%. The proposed method was finally applied to determination of As(III) in water samples with satisfactory results.

Tandem air-agitated liquid–liquid microextraction as an efficient method for determination of acidic drugs in complicated matrices

A rapid and simple microextraction method with a high sample clean-up, termed as tandem air-agitated liquid–liquid microextraction (TAALLME), is described. This method is based upon the tandem implementation of the air-agitated liquid–liquid microextraction (AALLME), and this approach improves the applicability of the dispersive liquid–liquid microextraction (DLLME) methods in complicated matrices. With very simple tools, the three non-steroidal anti-inflammatory drugs diclofenac, ibuprofen, and mefenamic acid were efficiently extracted, with an overall extraction time of 7 min. By performing the first AALLME, these acidic analytes, contained in an aqueous sample solution (donor phase, 8.0 mL), were extracted into the organic solvent (1,2-dichloroethane, 37 μL), and their simple back-extraction into the aqueous acceptor solution (pH, 10.01, 51 μL) was obtained in 2 min by a second implementation of AALLME. Response surface methodology (RSM) was used for optimization of the experimental parameters. The pH values 2.94 and 10.01 were obtained for the donor and acceptor phases, respectively, and the volumes 99.5 and 51 μL were obtained for the organic solvent and the acceptor phase, respectively, as the optimal extraction conditions. Under the optimized conditions, tandem AALLME-HPLC-UV provided a good linearity in the range of 0.5–4000 ng mL−1, limits of detection (0.1–0.3 ng mL−1), extraction repeatabilities (relative standard deviations (RSDs) below 7.7%, n = 5), and the enrichment factors (EFs) of 80–104. Finally, the applicability of the proposed method was evaluated by the extraction and determination of the drugs under study in the wastewater and human plasma samples.

Electromembrane extraction for the determination of parabens in water samples.

To our knowledge, for the first time an electromembrane extraction combined with a high-performance liquid chromatography procedure using diode-array detection has been developed for the determination of five of the most widely used parabens: ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, isobutyl 4-hydroxybenzoate, and benzyl 4-hydroxybenzoate. Parabens were extracted from pH 4 aqueous sample solutions with use of an Accurel® S6/2 polypropylene hollow fiber that supports a liquid membrane of 1-octanol to a pH 12 aqueous acceptor solution placed inside the lumen of the hollow fiber. An electric current of 30 V was applied over the supported liquid membrane by means of platinum wires placed in the donor and acceptor phases. Parabens were extracted in 40 min with enrichment factors in the 30-49 range. The procedure has detection limits between 0.98 and 1.43 μg L(-1). The method was applied to the determination of parabens in surface environmental waters with excellent results.

Dynamic electromembrane extraction: Automated movement of donor and acceptor phases to improve extraction efficiency

In the present research, dynamic electromembrane extraction (DEME) was introduced for the first time for extraction and determination of ionizable species from different biological matrices. The setup proposed for DEME provides an efficient, stable, and reproducible method to increase extraction efficiency. This setup consists of a piece of hollow fiber mounted inside a glass flow cell by means of two plastics connector tubes. In this dynamic system, an organic solvent is impregnated into the pores of hollow fiber as supported liquid membrane (SLM); an aqueous acceptor solution is repeatedly pumped into the lumen of hollow fiber by a syringe pump whereas a peristaltic pump is used to move sample solution around the mounted hollow fiber into the flow cell. Two platinum electrodes connected to a power supply are used during extractions which are located into the lumen of the hollow fiber and glass flow cell, respectively. The method was applied for extraction of amitriptyline (AMI) and nortriptyline (NOR) as model analytes from biological fluids. Effective parameters on DEME of the model analytes were investigated and optimized. Under optimized conditions, the calibration curves were linear in the range of 2.0–100μgL−1 with coefficient of determination (r2) more than 0.9902 for both of the analytes. The relative standard deviations (RSD %) were less than 8.4% based on four replicate measurements. LODs less than 1.0μgL−1 were obtained for both AMI and NOR. The preconcentration factors higher than 83-fold were obtained for the extraction of AMI and NOR in various biological samples.

In-tube electro-membrane extraction with a sub-microliter organic solvent consumption as an efficient technique for synthetic food dyes determination in foodstuff samples

A simple and efficient extraction technique with a sub-microliter organic solvent consumption termed as in-tube electro-membrane extraction (IEME) is introduced. This method is based upon the electro-kinetic migration of ionized compounds by the application of an electrical potential difference. For this purpose, a thin polypropylene (PP) sheet placed inside a tube acts as a support for the membrane solvent, and 30μL of an aqueous acceptor solution is separated by this solvent from 1.2mL of an aqueous donor solution. This method yielded high extraction recoveries (63–81%), and the consumption of the organic solvent used was only 0.5μL. By performing this method, the purification is high, and the utilization of the organic solvent, used as a mediator, is very simple and repeatable. The proposed method was evaluated by extraction of four synthetic food dyes (Amaranth, Ponceau 4R, Allura Red, and Carmoisine) as the model analytes. Optimization of variables affecting the method was carried out in order to achieve the best extraction efficiency. These variables were the type of membrane solvent, applied extraction voltage, extraction time, pH range, and concentration of salt added. Under the optimized conditions, IEME-HPLC-UV provided a good linearity in the range of 1.00–800ngmL−1, low limits of detection (0.3–1ngmL−1), and good extraction repeatabilities (RSDs below 5.2%, n=5). It seems that this design is a proper one for the automation of the method. Also the consumption of the organic solvent in a sub-microliter scale, and its simplicity, high efficiency, and high purification can help one getting closer to the objectives of the green chemistry.

Determination of phenazopyridine in biological fluids using electromembrane extraction followed by high-performance liquid chromatography

Recently, electro-assisted extraction of ionic drugs from biological fluids through a supported liquid membrane and into an aqueous acceptor solution was introduced as a new sample preparation technique and has been termed electromembrane extraction (EME). In the present work, this microextraction technique combined with high-performance liquid chromatography and ultraviolet detection has been developed for detection of phenazopyridine (PP) as a local analgesic drug in human plasma and urine samples. From a 6.5 mL neutral aqueous sample, PP was extracted for 20 min through a thin supported liquid membrane of 2-nitrophenyl octyl ether sustained in the pores of the wall of a porous hollow fiber and into an aqueous acidic acceptor solution (25 μL, containing negative electrode) by application of a DC electrical potential. The effects of several factors, including the nature of organic solvent, HCl concentration in donor and acceptor solutions, stirring speed, extraction time, and applied voltage on the extraction efficiency of the drug, were investigated and optimized. Satisfactory linearity ranges with correlation coefficients higher than 0.996 in different extraction media, admissible limits of detection (0.5 and 1.0 ng mL−1 in urine and plasma samples, respectively) and good repeatability and reproducibility (intra- and inter-assay precisions ranged between 3.7%–6.8% and 8.8%–12.5%, respectively) were obtained. The optimized EME procedure was applied to determine the concentration of PP in various matrices, such as plasma and urine samples, and satisfactory results were obtained.