Dextrin-assisted gel electromembrane extraction of chiral drugs: Improving the extraction efficiency and investigation of enantioselectivity of extraction.

The present study investigates the use of dextrins (maltodextrin, ß-cyclodextrin, and hydroxypropyl-ß-cyclodextrin) to improve the efficiency of the agarose-based gel electromembrane extraction technique for extracting chiral basic drugs (citalopram, hydroxyzine, and cetirizine). Additionally, it examines the enantioselectivity of the extraction process for these drugs. To achieve these, dextrins were incorporated into either the sample solution, the membrane, or the acceptor solution, and then the extraction procedure was performed. Enantiomers were separated and analyzed using a capillary electrophoresis device equipped with a UV detector. The results obtained under the optimal extraction conditions (sample solution pH: 4.0, acceptor solution pH: 2.0, gel membrane pH: 3.0, agarose concentration: 3 % w/v, stirring rate: 1000 rpm, gel thickness: 4.4 mm, extraction voltage: 62.3 V, and extraction time: 32.1 min) indicated that incorporating dextrins into either the sample solution, membrane or the acceptor solution enhances extraction efficiency by 17.3-23.1 %. The most significant increase was observed when hydroxypropyl-ß-cyclodextrin was added to the acceptor solution. The findings indicated that the inclusion of hydroxypropyl-ß-cyclodextrin in the sample solution resulted in an enantioselective extraction, yielding an enantiomeric excess of 6.42-7.14 %. The proposed method showed a linear range of 5.0-2000 ng/mL for enantiomers of model drugs. The limit of detection and limit of quantification for all enantiomers were found to be < 4.5 ng/mL and <15.0 ng/mL, respectively. Intra- and inter-day RSDs (n = 4) were less than 10.8 %, and the relative errors were less than 3.2 % for all the enantiomers. Finally, the developed method was successfully applied to determine concentrations of enantiomers in a urine sample with relative recoveries of 96.8-99.2 %, indicating good reliability of the developed method.

Thin-film solid-phase microextraction of pesticides from cereal samples using electrospun polyvinyl alcohol/modified chitosan/porous organic framework nanofibers.

In this study, a coating of electrospun polyvinyl alcohol/modified chitosan/hydroxy-containing porous organic framework (PVA/MCS/HC-POF) was fabricated and applied as a novel sorbent for thin-film solid-phase microextraction of pesticides from cereal samples, followed by HPLC-UV. The successful fabrication of PVA/MCS/HC-POF was confirmed through characterization tests. The functional group of MCS and a large number of hydroxyl groups on the HC-POF structure contributed to the co-extraction of pesticides. Under the optimum conditions, the calibration plots were linear within the range of 5.0-800 ng mL-1 (r2 ≥ 0.978), and the limits of detection were obtained below 4.0 ng mL-1. The method's precision was investigated through intra-day, inter-day, and film-to-film RSD (%) measurements, all of which were less than 6.5 %, 8.2 %, and 10.0 %, respectively. Furthermore, satisfactory recoveries ranging from 63.3 % to 79.0 % were obtained. Accordingly, the proposed method can be considered a suitable alternative for measuring trace amounts of pesticides in cereal samples.

Carboxymethylated maltodextrin as a chiral selector for the separation of some basic drug enantiomers using capillary electrophoresis.

In this work, carboxymethylated maltodextrin (Cm-MD) was successfully synthesized as an efficient anionic chiral selector and applied for the enantiomer separation of some basic drugs including tramadol, venlafaxine, verapamil, hydroxyzine, citalopram, fluoxetine, and amlodipine by capillary electrophoresis (CE). The synthesized chiral selector was characterized by the nuclear magnetic resonance and Fourier transform infrared spectrophotometry. Under the optimized Cm-MD modified CE conditions (background electrolyte: phosphate buffer (pH 5.0, 50 mM) containing 5% (w/v) Cm-MD; applied voltage: 20 kV; and capillary column temperature: 25 °C), successful enantiomer separation of all studied chiral drugs were observed. By comparison of Cm-MD and MD for enantiomer separation of the model drugs, it was revealed that Cm-MD exhibits a higher resolution in comparison to the MD modified CE. This enhanced resolution could be attributed to the electrostatic interactions between the cationic drugs and anionic Cm-MD and opposite direction mobility of the host-guest complex relative to the chiral analyte. The optimized Cm-MD modified CE method was successfully used for the assay of the enantiomers of citalopram and venlafaxine in commercial tablets. The proposed method showed the linear range of 5.0-150.0 mg/L and 10.0-150.0 mg/L for both enantiomers of citalopram and venlafaxine, respectively. The limits of quantification were 5.0 and 10.0 mg/L for the enantiomers of citalopram and venlafaxine, respectively. The limit of detection for all enantiomers was found to be < 3.0 mg/L. Intra- and inter-day RSDs (n = 4) were less than 9.7%. The relative errors were less than 9.4% for all enantiomers. The obtained results in this research show that Cm-MD as a new, efficient and inexpensive chiral selector can be used for enantiomer separation of basic drugs using the CE technique.

Green hydrophobic maltodextrin nanosponges for magnetic solid-phase extraction of hypothalamic peptides from plasma samples.

In this work, for the first time, magnetic-phthalated maltodextrin nanosponges (M-PAMDNSs) were synthetized and introduced as efficient and green sorbents. The integration of phthaloyl groups as hydrophobic moieties into networks of maltodextrin nanosponges provided good enrichment for hypothalamic-related peptides (HRPs). The synthesized materials were characterized by 1H nuclear magnetic resonance spectroscopy, water contact angle, attenuated total reflection-Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, pH point of zero charge, acid-base titration, field-emission scanning electron microscopy, Brunauer-Emmett-Teller, and vibrating sample magnetometer. Under the optimized conditions (sorbent amount: 5.0 mg, desorption solvent volume and type: 300 µL of methanol: H2O: trifluoroacetic acid, extraction time: 15 min, and desorption time: 10 min), the developed magnetic solid-phase extraction (MSPE) method in combination with HPLC-UV was used as a novel and sensitive analytical method for the determination of HRPs in plasma samples. The proposed MSPE-HPLC-UV method provided good linearity (1.5-500 ng mL-1 R2 ≥ 0.9988), low limits of detection (0.1-0.2 ng mL-1) and quantification (0.4-0.8 ng mL-1), desirable precision (RSD ≤ 8.8%, n ₌ 5), satisfactory enrichment factor (EFs ≥ 66.0), and well relative recoveries (92.8-108.8%). Overall, the established method effectively expanded the analytical potential of MSPE approach for the quantification of HRPs in biological 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.

Preparation of an efficient magnetic nano-sorbent based on modified cellulose and carboxylated carbon nano-tubes for extraction of pesticides from food and agricultural water samples before GC-FID analysis.

This paper reports the direct synthesis approach of carboxamide functionalized magnetic nano-composite named Fe3O4@SiO2-NH2@dialdehyde cellulose (DAC)@CNT-COOH as an effectual sorbent for the co-extraction of seven agricultural insecticides and herbicides from vegetable, fruit, and water samples using the magnetic dispersive micro-solid-phase extraction procedure. Under the optimized extraction conditions (sorbent amount: 18.1 mg; desorption time: 6.5 min; desorption solvent volume: 185 µL; desorption solvent: acetonitrile; extraction time: 9.5 min; pH of sample solution: 7.0, and salt content: 5.0 % w/v sodium chloride), good linearity within the range 0.5-1200 ng/mL (R2 ≥ 0.998) was achieved. Extraction efficiencies were in the range 63.4-84.1 %, the limits of detection were 0.08-1.0 ng/mL, and acceptable relative recoveries (87.6-103.8 %), and precisions were also achieved (RSDs < 6.8 %, n = 3). Ultimately, the obtained results showed that the developed method could be applied to determine trace amounts of desired analytes in various agricultural water and food 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.

Introduction of maltodextrin nanosponges as green extraction phases: Magnetic solid phase extraction of fluoroquinolones.

In the present work, for the first time, fully green maltodextrin nanosponges (MDNSs) as extraction phases for the preparation of magnetic sorbents were introduced. All of the raw materials and synthetic methodologies used to prepare MDNSs follow the principles of green chemistry. Fluoroquinolones (FQs) (ofloxacin, ciprofloxacin, enrofloxacin, and moxifloxacin) were used as model analytes to assess the extraction performance of MDNSs in magnetic solid-phase extraction (MSPE) procedure. Under the optimized conditions, the developed MSPE was coupled with HPLC-UV to sensitively quantify trace levels of four FQs in tap water, wastewater, and river water samples. The proposed MSPE-HPLC-UV method provided wide linearity in the range of 0.25-500.0 ng mL-1 with determination coefficients ≥0.9997. Low limits of detection (LODs ≤0.06 ng mL-1) and quantification (LOQs ≤0.20 ng mL-1) were achieved. Furthermore, the developed green extraction phases compared with all other maltodextrin-based extraction phases were promising.

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.

Preparation of electrospun polyacrylonitrile/ϒ-cyclodextrin metal-organic framework nanofibers for extraction of multi-classes herbicides from cereal samples before HPLC-UV analysis.

This study employed thin-film solid-phase microextraction procedure as a simple, sensitive, green, and solvent-free method for the co-extraction of multi-classes herbicides from cereal samples before HPLC-UV analysis. To provide an efficient sorbent, electrospun nanofibers of the crosslinked polyacrilonitril/ϒ-cyclodextrin-metal-organic framework (PAN/ϒ-CD-MOF) were successfully fabricated and assessed as a new thin-film adsorbent. Under the optimal conditions (desorption solvent: acetonitrile, desorption time: 5 min, sample solution pH: 7.0, salt concentration: 15% (w/w), and extraction time: 15 min), good linearity in the range of 2.5-1250.0 ng/mL (r2 ≥ 0.992) was obtained. The detection limits were 0.75-2.50 ng/mL. The extraction recoveries and relative recoveries were 64.9-75.7% and 92.9-106.1%, respectively. The method showed good precision as the relative standard deviations were ≤ 6.3%. Finally, the developed method was applied efficiently for trace analysis of the herbicides in wheat, rice, and barley samples. Generally, the proposed method provided a simple, sensitive, environmentally friendly, and relatively fast approach.

Selective extraction and determination of Cr(VI) in food samples based on tandem electromembrane extraction followed by electrothermal atomic absorption spectrometry.

In this study, electromembrane extraction (EME) combined with micro-EME (µ-EME) was used for the selective extraction of Cr(VI) from food samples (milk powder, Ocimum basilicum, and fish samples). Electrothermal atomic absorption spectrometry was used for the quantification of Cr(VI). Under the optimized extraction conditions, the extraction recovery of Cr(VI) was 73.7%. This proposed method provided a linear range from 0.01 to 5.0 ng/mL and the limit of detection (LOD) and limit of quantification (LOQ) were 0.003 and 0.010 ng/mL. The %RSD (n = 5) was in the range of 11.2-11.8% at 0.05, 1.0 and 2.5 ng/mL of Cr(VI), and the enrichment factor was 584. The accuracy of the method was evaluated by analysis of SRM 2700 as a certified reference material (CRM) and result was in good agreement with the certified value.

Magnetic solid-phase extraction of high molecular weight peptides using stearic acid-functionalized magnetic hydroxyapatite nanocomposite: determination of some hypothalamic agents in biological samples.

Therapeutic peptides have an important effect on physiological function and human health, so it is momentous to quantify and detect low levels of these biomolecules in biological samples for treatment and diagnostic purposes. In the present study, an efficient magnetic solid-phase extraction (MSPE) method was developed based on stearic acid-functionalized magnetic hydroxyapatite nanocomposite (MHAP/SA) as a novel and cost-effective adsorbent for extraction of five hypothalamic-related peptides (goserelin, octreotide, triptorelin, somatostatin, and cetrorelix) from biological samples. To characterize the morphology and physicochemical properties of MHAP/SA, Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDS), field emission scanning microscopy (FE-SEM), CHNS elemental analysis, Brunauer-Emmett-Teller (BET), and vibrating sample magnetometry (VSM) were applied. Under optimum conditions, the proposed method (MSPE-HPLC-UV) represented favorable linearity with R2 ≥ 0.9987, suitable intra- and inter-day precisions (RSD ≤ 6.9% and RSD ≤ 8.1%, respectively, n = 3), and limits of detection and quantification in the range of 0.75-1.12 ng mL-1 and 2.50-3.75 ng mL-1, respectively. Eventually, the proposed method was used for the extraction and quantification of target therapeutic peptides in plasma and urine samples, and satisfactory relative recoveries were achieved in the range of 90.6-110.3%.

Magnetic dispersive solid-phase extraction of triazole and triazine pesticides from vegetable samples using a hydrophilic-lipophilic sorbent based on maltodextrin- and ß-cyclodextrin-functionalized graphene oxide.

Maltodextrin- and ß-cyclodextrin-functionalized magnetic graphene oxide (mGO/ß-CD/MD), a novel hydrophilic-lipophilic composite, was successfully fabricated and used for the co-extraction of triazines and triazoles from vegetable samples before HPLC-UV analysis. mGO/ß-CD/MD was synthesized by chemical bonding of ß-CD and MD to the surface of mGO, using epichlorohydrin (ECH) as a linker. The successful synthesis of mGO/ß-CD/MD was confirmed by characterization tests, including attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Barrett-Joyner-Halenda (BJH) analyses. The hydrophobic cavity of ß-CD and a large number of hydroxyl groups on the MD structure contributed to the co-extraction of mentioned pesticides with a wide range of polarity. Under the optimized condition (sorbent amount, 30 mg; desorption time, 10 min; desorption solvent volume, 300 µL; desorption solvent, methanol/acetonitrile (1:1) containing 5% (v/v) acetic acid; extraction time, 20 min; and pH of sample solution, 7.0), good linearity within the range 1.0-1000 µg L-1 (r2 ≥ 0.992) was achieved. Extraction efficiencies were in the range 66.4-95.3%, and the limits of detection were 0.01-0.08 µg L-1. Relative recoveries for spiked samples were obtained in the range 88.4-112.0%, indicating that the matrix effect was insignificant, and good precisions (intra- and inter-day) were also achieved (RSDs < 9.0%, n = 3). The results confirmed that the developed method was efficient for the determination  of trace amounts of pesticides in potato, tomato, and corn samples.

Development of electrically assisted solvent bar microextraction followed by high performance liquid chromatography for the extraction and quantification of basic drugs in biological samples.

In this study, a new extraction procedure is introduced based on electrically assisted solvent bar microextraction. In the first step, the analytes are transferred from sample solution to the hollow fiber supported organic solvent. After that, with the aid of an electrical field, the analytes migrated into the aqueous extractant. The proposed approach was used to extract the three basic drugs (including lidocaine, diltiazem, and propranolol) from the plasma and urine samples. Under the optimized condition, (the supported organic solvent: 1-octanol, stirring rate: 300 rpm, pH of sample solution: 12.0, salt concentration: 2.0% (w/v), extraction time: 15 min, aqueous extractant: (30 µL, 100 mM HCl), back-extraction time: 2 min, back-extraction voltage: 100 V), the proposed procedure presented wide linearities with coefficients of determination more than 0.992 over a concentration range of 5.0-1000 ng mL-1. The limit of detection was also determined in the range of 0.5 to 5.0 ng mL-1, repeatability (intra-day) was between 3.3 and 11.1% (n = 4), and reproducibility (inter-day) was between 4.3 and 14.6% (n = 4 days). It was indicated that the proposed approach could effectively extract the analytes from the plasma and urine samples, and the relative recoveries were between 90.2 and 105.6%, indicating the validity of this method.

Recent advances and applications of cyclodextrins in magnetic solid phase extraction.

Cyclodextrins (CDs) as a family of cyclic oligosaccharides are toroidal with a hydrophobic interior and a hydrophilic exterior. They are well-known for their ability to form host-guest inclusion complexes with different compounds. They are used as chiral stationary phases in high performance liquid chromatography (HPLC) and gas chromatography (GC) or as chiral reagents in the background electrolyte of capillary electrophoresis (CE). In recent years, they have been used for modification of sorbents or as sorbents in solid phase extraction (SPE) procedures. Magnetic solid-phase extraction (MSPE), as a new type of SPE procedure, has received considerable attention due to its rapid phase separation process as compared to traditional extraction mode. This review covers the synthesis of CD-based magnetic sorbents (such as immobilization of CDs onto the different supports, production of nanosponges, and making hybrid substances with nanomaterials) and the use of these compounds in MSPE of different analytes from biological, environmental, and food samples. Also, prospects of CD-based sorbents for sample pre-treatment are also proposed.

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.

Graphene quantum dots based on maltose as a high yield photocatalyst for efficient photodegradation of imipramine in wastewater samples.

PURPOSE: In this work, for the first time, graphene quantum dots (GQDs) based on maltose were fabricated as a new photocatalytic material to the photodegradation of imipramine (as a persistence organic pollutant) under light irradiation. METHODS: The synthesized GQDs were characterized by different instrumentation approaches such as X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), nitrogen adsorption/desorption, and transmission electron microscopy (TEM). A Box-Behnken design (BBD) and the response surface methodology (RSM) were applied for the optimization of different factors that affect the overall photocatalytic yield. RESULTS: Under the optimized conditions (pH of the sample solution: 2.0; photocatalyst dosage: 0.1 mg mL-1; UV exposure time: 80 min), the highest achievable reduction efficiency was obtained about 80%. The stability and reusability of the synthesized photocatalytic material were investigated in four reaction cycles (80 min), which showed only a 15% photo-activity loss after the fourth photocatalytic runs. CONCLUSIONS: The proposed method was successfully applied to degrade the mentioned drug in the real wastewater samples by about 70%. Regarding the mentioned advantages by the proposed method, this new kind of photocatalytic material possesses a strong potential for photodegradation of pollutants in industrial wastewater samples. GRAPHICAL ABSTRACT: Photodegradation of imipramine using graphene quantum dots based on maltose.

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.

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.

Gel-electromembrane extraction of peptides: Determination of five hypothalamic agents in human plasma samples.

Agarose gel as a green membrane has been proposed for use in electromembrane extraction of five hypothalamic-related peptides without an ionic carrier. Octreotide, goserelin, triptorelin, cetrorelix, and somatostatin were extracted from 5.0 mL of sample solution (adjusted to pH 5.0) into a microvolume acceptor solution (HCl, 100 mM) under the applied voltage of 30 V in 15 min. The pH of the agarose gel 3.0% (w/v) was adjusted to 4.0 to facilitate the movement of peptides through the membrane. Quantification was performed using an HPLC-UV system on a C18 column. Quantification and detection limits were found to be in the range of 15.0-20.0 ng mL-1 and 4.5-6.0 ng mL-1, respectively. Dynamic linear ranges were found to be in the range of 15.0-1000 ng mL-1 (R2 > 0.995) and recoveries were in the range of 62.3-77.6%. The optimized method was applied to spiked human plasma samples. The method showed relative recoveries in the range of 44.8-66.0%. Finally, the proposed method was compared with and shown to have higher recoveries than, the conventional electromembrane extraction method for the peptides under study.