Application of oxygen scavengers in gel electromembrane extraction: A green methodology for simultaneous determination of nitrate and nitrite in sausage samples.

The generation of oxygen from electrolysis in gel electromembrane extraction (G-EME) causes a negative error when applied to the analysis of easily oxidized species such as nitrite. Nitrite in G-EME is oxidized by oxygen to nitrate, leading to the negative error and the impossibility of simultaneous analysis. In this work, the application of oxygen scavengers to the acceptor phase of the G-EME system was attempted to minimize the oxidation effect. Several oxygen scavengers were selected and examined according to their compatibility with ion chromatography. The mixture of sulfite and bisulfite (14 mg L-1) showed the highest efficiency in preventing the oxidation of nitrite to nitrate. Under the optimized conditions, a good linear range was obtained (10-200 µg L-1; R2 > 0.998) with a detection limit of 8 µg L-1 for both nitrite and nitrate. This method was applied to the simultaneous determination of nitrite and nitrate in sausage samples.

Liquid-Phase Microextraction Approaches for Preconcentration and Analysis of Chiral Compounds: A Review on Current Advances.

Chirality is a critical issue in pharmaceutics, forensic chemistry, therapeutic drug monitoring, doping control, toxicology, or environmental investigations as enantiomers of a chiral compound can exhibit different activities, i.e., one enantiomer can have the desired effect while the other one can be inactive or even toxic. To monitor enantioselective metabolism or toxicokinetic/toxicodynamic mechanisms in extremely low content in biological or environmental matrices, sample preparation is vital. The present review describes current status of development of liquid-phase microextraction approaches such as hollow fiber liquid-phase microextraction (HF-LPME), electromembrane extraction (EME), dispersive liquid-liquid microextraction (DLLME), and supramolecular solvent-based microextraction (SSME), used for sample preparation of enantiomers/chiral compounds. The advantages and limitations of the above techniques are discussed. Attention is also focused on chiral separation approaches commonly applied to study the stereo-selective metabolism or toxicokinetic/toxicodynamic mechanisms of enantiomers in the biological and environmental samples.

In-tube gel electromembrane extraction: A green strategy for the extraction of narcotic drugs from biological samples.

The development of green and miniature extraction methods is always a major and controversial challenge in the field of sample preparation. In this work, in-tube gel electromembrane extraction (IT-G-EME) was developed as a miniaturized extraction device for the extraction of six narcotic drugs (codeine, oxycodone, hydrocodone, tramadol, thebaine, and noscapine) from biological samples. A transparent capillary tube (∼6 cm) was used as a microextraction unit. The middle part of the tube was filled with a narrow plug (∼3 mm) of the agarose gel (3.0% w/v) as a membrane and the other sides were filled with aqueous extractant solution (pH 2.0, 20 µL) and sample solution (pH 5.0, 200 µL). By applying electrical potential (400 V), the target drugs with positive charge were migrated from sample solution toward the extractant solution through gel membrane during short extraction time (5 min). Then, the enriched analytes in extractant solution was analyzed by HPLC-UV. Under the optimized conditions, the calibration curves were linear within the permissible range of 10.0-1500 ng/mL (r2 ≥ 0.991). Limits of detection and extraction recoveries were in the range of 3.0-4.5 ng/mL and 61.9-86.9%, respectively. On the basis of four replications, the repeatability of the method was also evaluated in terms of intra- and inter-day RSDs (%), which did not exceed from 6.6 and 7.9%, respectively in aqueous media. The figures of merit were also assessed in biological samples. Eventually, the developed method was profitably used for simultaneous determination of narcotic drugs in the real urine and plasma samples.

Evaluation of complexing agents in the gel electro-membrane extraction: An efficient approach for the quantification of zinc (II) ions in water samples.

In this work, gel electro-membrane extraction (G-EME) combined with flame atomic absorption spectrometry (FAAS) was used for the determination of zinc ions (Zn2+) in water samples. For the first time, the effect of the presence of three types of complexing agents such as phenanthroline (Phen), crown ethers (12C4, 15C5, 18C6), and ethylene-diamine-tetra-acetic acid (EDTA) on the extraction efficiency of zinc ions was studied. In addition, the electroendosmosis (EEO) flow as an unwanted actuator was monitored in the presence and absence of complexing agents. By applying 50 V electrical potential across the membrane, the positive charged Zn2+ ions were migrated from a donor phase (pH 5.0) through the agarose gel membrane (pH 5.0, containing a complexing agent) into the acceptor phase (pH 3.0). The obtained results showed that the highest extraction recoveries were obtained when crown ethers, especially 1% (w/v) 18C6 was added to the gel membrane. In addition, EEO flow was decreased in the presence of all complexing agents (except EDTA), probably due to the increase in electrical resistance. Using the optimum conditions, the limit of detection (LOD), the limit of quantification (LOQ), and extraction recovery% (ER%) were 5.0 µg L-1, 15.0 µg L-1, and 92.5%, respectively. In the end, the applicability of the developed approach was successfully evaluated to determine Zn2+ in tap, mineral, and river water samples.

Introduction of nitrogen doped graphene nanosheets as efficient adsorbents for nitrate removal from aqueous samples.

PURPOSE: Introducing and developing new kinds of adsorbents are always a significant challenge in water treatments. In this work, for the first time, graphene oxide (GO), nitrogen-doped graphene oxide (ND-GO), highly nitrogen-doped graphene oxide (HND-GO), and 3D high nitrogen-doped graphene oxide (3D-HND-GO) were synthesized and comparatively evaluated in the removal of nitrate content of tap and underground waters. METHODS: The removal of the target analyte was performed through a batch adsorption approach, and the factors influencing its removal efficiency (i.e., initial pH of the sample, primary concentrations of nitrate, amount of adsorbent, and contact time) were evaluated through a central composite design (CCD) and response surface methodology (RSM). RESULTS: Based on the results, 3D-HND-GO showed the highest removal efficiency in comparison with the other mentioned nanoparticles. The nitrate removal using this adsorbent was modeled successfully so that R 2, adjusted R 2, and predicted R 2 values were 0.9717, 0.9508, and 0.9010, respectively. In addition, the optimal removal condition was achieved using the Nelder-Mead non-linear optimization algorithm as follow: the initial concentrations of nitrate (expressed as nitrogen): 15.0 mg/mL, the amount of the adsorbent: 2.0 mg/mL; pH of the sample: 3.0; and the contact time: 20.0 min. Under this optimal condition, the actual removal result (92.5 ± 4.0%) was in good agreement with the expected value (94.8 ± 5.1%). Additional studies were also performed to comprehensibly evaluate the adsorption activity of the adsorbent (e.g., kinetic, isotherm, and desorption parameters). The adsorption isotherm complied with the Langmuir model illustrating the considerable mono-layer adsorption capacities for the target ions with qm of 8.7 mg/g. The adsorption process was indicated to obey a pseudo 2nd order kinetic model, with the rate-limiting step for the adsorption phase. CONCLUSIONS: This study revealed which 3D-HND-G leads to improved yield in the nitrate ions elimination, particularly at acidic media, which was related to the enhanced dispersibility and larger surface area. The adsorbent was further successfully used for treating tap and underground water samples. At the present moment, research as grown to modify 3D-HND-G in orders to increase the potentiality for industrial applications. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40201-021-00741-7.

A low-voltage electro-membrane extraction for quantification of imatinib and sunitinib in biological fluids.

Aim: Hollow-fiber-based supported liquid membrane was modified utilizing nanostructures such as graphite, graphene oxide or nitrogen-doped graphene oxide, for electro-membrane extraction (EME) of imatinib and sunitinib from biological fluids. By applying these conductive nanostructures, a low-voltage EME device (6.0 V) was fabricated. Materials & methods: A response surface methodology through central composite design was used to evaluate and optimize effects of various essential factors that influence on normalized recovery. Results: Optimal extraction conditions were set as, 1-octanol with 0.01 % (w/v) graphene oxide functioning as the supported liquid membrane, an extraction time of 17.0 min, pH of the acceptor and the donor phase of 2.8 and 7.9, respectively. Conclusion: The method was successfully applied to quantify imatinib and sunitinib in biological fluids.

Gel electromembrane microextraction followed by ion chromatography for direct determination of iodine in supplements and fortified food samples: Green chemistry for food analysis.

In this study, a sensitive, selective, and environmentally friendly analytical method for direct extraction and preconcentration of iodine was developed. Iodine, as an iodate ion or iodide ion, was simultaneously extracted and preconcentrated by gel electromembrane microextraction (G-EME) and analyzed for total iodine by ion chromatography. The total iodine was determined by combining the peak areas of both iodate and iodide ions. Under the optimized conditions, linear calibration for iodine using a mixture of iodate and iodide ions was obtained from 10 to 100 µg L-1 (r2 > 0.996). The detection limit was 7.0 µg L-1. Recoveries of spiked iodine (as iodate) in the samples were greater than 90%. The method was applied for the determination of iodine in dietary supplements and fortified food samples, i.e., iodine-enriched eggs. Our developed method could be directly applied for the determination of iodine in different matrix samples including eggs without a pretreatment step.

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.

An overview on the recent applications of agarose as a green biopolymer in micro-extraction-based sample preparation techniques.

Introducing a myriad array of chemicals in different industrial fields has made sample preparation inevitable for trace analysis. Classical extraction techniques such as solid phase extraction (SPE) and liquid-liquid extraction (LLE) techniques often suffer from tedious procedures (huge workload) and hazards to personnel and environment (samples and reagents are often user-unfriendly and processed in high amounts). For addressing these problems, microextraction techniques have been introduced. These systems benefit from using a minute amount of sample, reduced consumption of organic solvents, enhanced clean-up, high recovery and high enrichment factors. Moreover, approaches based on the use of natural materials have emerged during the last 10 years. Agarose is a natural biopolymer used as a green material in the form of gel-based separation medium. It has been recently utilized in the microextraction schemes. Easy fabrication, adjustability to get various dimensions and shapes, high inertness and biodegradability are of its main attributes. The present overview is focused on applications of agarose in solid phase microextraction (SPME), micro-solid phase extraction (µ-SPE) and liquid phase microextraction (LPME) - agarose film-liquid phase microextraction (AF-LPME) and gel electromembrane extraction (G-EME) since 2012. Besides, the pros and cons of agarose employment in the mentioned techniques will be described in depth.

Gel electro-membrane extraction of propranolol and atenolol from blood serum samples: Effect of graphene-based nanomaterials on extraction efficiency of gel membrane.

In this work, gel electro-membrane extraction (G-EME) method is suggested for extraction and determination of propranolol and atenolol in complex biological samples. An in-house membrane based on agarose was used as green and biodegradable gel membrane. Essential chemical parameters that influence on extraction efficiency were tested, optimized and evaluated via a central composite design (CCD) and response surface methodology (RSM). Optimal conditions for extraction of drugs from the 7.0 mL sample were as follows: 3% (w/v) agarose with 0.1% (v/v) acetic acid functioning as membrane, voltage: 50 V; pH of the donor phase (DP): 8.1; pH of the AP: 3.3; extraction time: 35.9 min. Under these conditions, the acceptable normalized extraction recoveries were obtained such as 71.9 ± 5.4% that were in good agreement with the predicted values (i.e., 73.1 ± 0.9%). Limits of detection (LODs) for propranolol and atenolol were 5.0 ng mL-1 and 7.5 ng mL-1, respectively. Moreover, for the first time, the effect of presence of four graphene-based nanomaterials such as graphene (G), graphene oxide (GO), three-dimensional nitrogen doped graphene oxide (3D-ND-GO) and high nitrogen doped graphene oxide (HND-GO) in agarose gel membrane on extraction efficiency, was investigated. The results showed that in presence of these nanomaterials, the normalized recovery depressed significantly due to increasing of electric current and electroendosmosis (EEO) phenomenon. Eventually, the proposed method was applied to quantify basic drugs in real plasma samples with relative recoveries in the range of 85.7-97.5%, indicating good reliability of the assay.

Gel electromembrane extraction using rotating electrode: A new strategy for mass transfer enhancement of basic drugs from real human urine samples.

This study proposed a new method of EME based on agarose gel named rotating electrode gel electromembrane extraction (RE-G-EME) for extraction and determination of naloxone, naltrexone, and nalbuphine as basic drugs from real human urine samples. In this new method, a rotating electrode connected to the armature was used to agitate the acceptor phase (AP). With this new development, the extraction efficiency enhanced due to increasing analytes mass transfer from gel membrane interface toward the AP. The effective parameters on the extraction efficiency were optimized and the maximum recoveries of the analytes were obtained under the optimal extraction conditions (3.0% (w/v) agarose with pH 5.0 as gel membrane; voltage: 25 V; pH of the donor phase (DP): 6.0; pH of the AP: 4.0; stirring rate of the DP: 750 rpm; electrode rotation speed within AP: 125 rpm; extraction time: 25 min). The method offered limits of detection (LODs) and extraction recoveries in the range of 0.3-1.5 ng mL-1, and 74.3% - 87.0%, respectively. Also, the repeatability of the proposed method was measured for four repeated experiments and was in the acceptable range of 4.3% - 8.1%. To understand the influence of agitation of the AP on the extraction efficiency, a comparative study was carried out between conventional G-EME and RE-G-EME methods. The results showed that, for short the extraction times (t ≤ 10 min), extraction efficiency of G-EME was almost the same as that of RE-G-EME. However, at longer extraction times (25 min), the extraction efficiency of RE-G-EME was significantly higher than that of G-EME. Finally, the proposed method was successfully applied to determine concentrations of model drugs in real urine samples with relative recoveries of 81.1-96.1% indicating good reliability of the proposed method.

Recent advances in robotic protein sample preparation for clinical analysis and other biomedical applications.

Discovery of new protein biomarker candidates has become a major research goal in the areas of clinical chemistry, analytical chemistry, and biomedicine. These important species constitute the molecular target when it comes to diagnosis, prognosis, and further monitoring of disease. However, their analysis requires powerful, selective and high-throughput sample preparation and product (analyte) characterisation approaches. In general, manual sample processing is tedious, complex and time-consuming, especially when large numbers of samples have to be processed (e.g., in clinical studies). Automation via microtiter-plate platforms involving robotics has brought improvements in high-throughput performance while comparable or even better precisions and repeatability (intra-day, inter-day) were achieved. At the same time, waste production and exposure of laboratory personnel to hazards were reduced. In comprehensive protein analysis workflows (e.g., liquid chromatography-tandem mass spectrometry analysis), sample preparation is an unavoidable step. This review surveys the recent achievements in automation of bottom-up and top-down protein and/or proteomics approaches. Emphasis is put on high-end multi-well plate robotic platforms developed for clinical analysis and other biomedical applications. The literature from 2013 to date has been covered.

Inside gel electromembrane extraction: A novel green methodology for the extraction of morphine and codeine from human biological fluids.

In this work, a new mode of gel-electromembrane extraction (G-EME), called "inside" gel-EME (IG-EME) is proposed for the extraction of morphine and codeine as model basic drugs from complex biological samples. Here, an aqueous media that was captured inside the agarose gel membrane, acted as both gel membrane and the acceptor phase (AP) at the same time. In this regard, the membrane served as the separation filter (membrane) and supported liquid acceptor phase (SLAP) as well. With this new development, unwanted changes of the AP volume during the extraction, which is a common issue in the G-EME (due to electroendosmosis (EEO) phenomenon), was addressed properly. Briefly, the setup involved insertion of negative electrode inside the gel membrane and positive electrode into the donor phase (DP). Following that, the IG-EME was easily performed using optimal conditions (pH of the DP: 6.0; membrane composition (agarose concentration: 1% (w/v) in aqueous media with pH 3.0, and 15 mm thickness); voltage: 25 V; and extraction time: 30 min). After extraction, the agarose gel was withdrawn and centrifuged for 5 min with 12000 rpm, to disrupt its framework to release the "trapped aqueous AP" apart from the gel structure. The separated AP was finally injected into the HPLC-UV for the analysis. The limits of detection (LODs) and recoveries in this proposed method were obtained 1.5 ng mL-1 and 67.7 %-73.8 %, respectively. The system feasibility was examined by the quantification of model drugs in the real plasma and urine samples.

Evaluation of dispersive liquid-liquid microextraction by coupling with green-based agarose gel-electromembrane extraction: An efficient method to the tandem extraction of basic drugs from biological fluids.

Nowadays, developing new methods for the effective extraction/separation of drugs (present at trace levels) from complicated matrices (as biological fluids) is certainly a great challenge for many operators. In this regard, green-based agarose gel electromembrane extraction (G-EME) was for the first time combined with dispersive liquid-liquid microextraction (DLLME) toward G-EME/DLLME methodology (i.e., tandem extraction approach). Two basic drugs such as trimipramine (TRI) and clomipramine (CLO) extracted from the urine samples, were used as model compounds. Regarding method workflow, analytes were extracted from the 5 mL sample, through a synthesized agarose gel membrane, to the 700 µL aqueous acceptor phase under the optimized conditions (pH of acceptor phase: 2.0; pH of gel membrane: 2.0; pH of donor phase: 4.0, voltage value: 30 V, and extraction time: 25 min). In the next step, acceptor solution was poured to a conic vial and mixed with 100 µL alkaline solution (NaOH, 1 M). Afterwards, DLLME procedure took place again at optimal conditions, i.e., extraction solvent was carbon tetrachloride (10 µL), and dispersive solvent was acetone (100 µL). Ultimately, gas chromatography (GC) was applied for the detection and quantification of drugs. Such G-EME/DLLME configuration has brought two main advantages. Firstly, interferences such as proteins and other large biological molecules were eliminated from biological fluids via G-EME. Further, high enrichment factors (EFs of 260-370 refer to extraction recoveries of 52-74%) were obtained using DLLME with acceptable detection limits (1.0-3.0 ng mL-1). Finally, the suggested approach was successfully utilized to determine drugs at trace levels in urine samples.

Recent developments in green membrane-based extraction techniques for pharmaceutical and biomedical analysis.

Monitoring of target analytes (e.g., pharmaceuticals, endogenous compounds) present in biological samples usually requires a preliminary step toward analyte isolation from surrounding matrix and enrichment for trace analysis. Evident developments have been recently made to introduce novel "green" analytical approaches (which keep the requirements of Green Analytical Chemistry - GAC) being effective, economical, eco-friendly, and amenable to hyphenated analytical instrumentations. Modern membrane-based extraction techniques provide the smart options against classical sample preparations e.g., liquid-liquid extraction (LLE).These approaches are more stable and allow trace determination of analytes in complex matrices (e.g., biological samples), with high extraction recovery and selectivity. Simultaneously, drawbacks of LLE such as large consumption of organic solvents and the need for tedious handling are eliminated. This paper thoroughly overviews important features and applications of membrane- based extraction techniques with special focus on pharmaceutical and biomedical analysis since 2013. Different driving forces of mass transfer across the membrane were summarized and membrane-based extraction techniques were described along with their advantages/disadvantages as well.

Separation of enantiomers of selected chiral sulfoxides with cellulose tris(4-chloro-3-methylphenylcarbamate)-based chiral columns in high-performance liquid chromatography with very high separation factor.

The present study reports successful separations of enantiomers of selected chiral sulfoxides with very high separation factor in high-performance liquid chromatography by using chiral columns prepared with the chiral selector cellulose tris(4-chloro-3-methylphenylcarbamate). High separation factors were observed in polar organic, as well as in hydrocarbon-alcohol-type mobile phases. The key structural components of the solute for obtaining high chiral recognition are discussed as well as thermodynamic quantities of analyte adsorption on the chiral stationary phase were determined. Experiment aimed at the enantioselective extraction of racemates from solution are also described.

Electro-driven extraction of polar compounds using agarose gel as a new membrane: Determination of amino acids in fruit juice and human plasma samples.

In this work, polypropylene hollow fiber was replaced by agarose gel in conventional electro membrane extraction (EME) to develop a novel approach. The proposed EME method was then employed to extract two amino acids (tyrosine and phenylalanine) as model polar analytes, followed by HPLC-UV. The method showed acceptable results under optimized conditions. This green methodology outperformed conventional EME, and required neither organic solvents nor carriers. The effective parameters such as the pH values of the acceptor and the donor solutions, the thickness and pH of the gel, the extraction voltage, the stirring rate, and the extraction time were optimized. Under the optimized conditions (acceptor solution pH: 1.5; donor solution pH: 2.5; agarose gel thickness: 7mm; agarose gel pH: 1.5; stirring rate of the sample solution: 1000rpm; extraction potential: 40V; and extraction time: 15min), the limits of detection and quantification were 7.5ngmL-1 and 25ngmL-1, respectively. The extraction recoveries were between 56.6% and 85.0%, and the calibration curves were linear with correlation coefficients above 0.996 over a concentration range of 25.0-1000.0ngmL-1 for both amino acids. The intra- and inter-day precisions were in the range of 5.5-12.5%, and relative errors were smaller than 12.0%. Finally, the optimized method was successfully applied to preconcentrate, clean up, and quantify amino acids in watermelon and grapefruit juices as well as a plasma sample, and acceptable relative recoveries in the range of 53.9-84.0% were obtained.

Application of polyacrylamide gel as a new membrane in electromembrane extraction for the quantification of basic drugs in breast milk and wastewater samples.

Introducing new membranes with green chemistry approach seems to be a great challenge for the development of a practical method in separation science. In this regard, for the first time, polyacrylamide gel as a new membrane in electromembrane extraction (EME) was used for the extraction of three model basic drugs (pseudoephedrine (PSE), lidocaine (LID), and propranolol (PRO)), followed by HPLC-UV. In comparison with conventional EME, in this method neither organic solvent nor carrier agents were used for extraction of mentioned drugs. Different variables for fabrication of polyacrylamide gel and extraction process were evaluated. Polyacrylamide gel (containing 12% (w/v) acrylamide, and 3.0% (w/w) bisacrylamide) with 2 mm thickness at pH = 1.5 was fabricated as membrane. The drugs were extracted from aqueous samples, through a polyacrylamide gel membrane, to an aqueous acceptor phase on membrane. Under the optimized extraction conditions (Voltage: 85 V, extraction time: 28 min, acceptor phase's pH: 4.0, and donor phase's pH: 7.0) limits of quantification and detection were in the ranges of 1.0-20.0 ng mL-1 and 0.3-6.0 ng mL-1, respectively. Applying the proposed method to determine and quantify intended drugs in breast milk, and wastewater samples have revealed acceptable results.

Introduction of agarose gel as a green membrane in electromembrane extraction: An efficient procedure for the extraction of basic drugs with a wide range of polarities.

Developing green methods for analyte extraction is one of the most important topics in the field of sample preparation. In this study, for the first time, agarose gel was used as membrane in electromembrane extraction (EME) without using any organic solvent, for the extraction of four model basic drugs (rivastigmine (RIV), verapamil (VER), amlodipine (AML), and morphine (MOR)) with a wide polarity window (log P from 0.43 to 3.7). Different variables playing vital roles in the proposed method were evaluated and optimized. As a driving force, a 25V electrical field was applied to make the analyte migrate from sample solution with pH 7.0, through the agarose gel 3% (w/v) with 5mm thickness, into an acceptor phase (AP) with pH 2.0. The best extraction efficiency was obtained with an extraction duration of 25min. With this new methodology, MOR with high polarity (log P=0.43) was efficiently extracted without using any carrier or ion pair reagents. Limits of detection (LODs) and quantification (LOQs) were in the ranges of 1.5-1.8ngmL-1 and 5.0-6.0ngmL-1, respectively. Finally, the proposed method was successfully applied to determine concentrations of the model drugs in the wastewater sample.

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.