The potential of application of an electrospun nanofiber sheet as new polymeric support for immobilizing the liquid membrane, instead of a common commercial polypropylene sheet, in on-chip ...electromembrane extraction (EME) of some acidic polar drugs followed by HPLC with ultraviolet detection is presented. The nanofiber sheet was prepared by electrospinning a mixture of polycaprolactone and polyaniline. The successful synthesis of the electrospun nanofiber sheet was confirmed by field emission-scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, and atomic force microscopy. Several parameters affecting the efficiency of the microextraction method, including pHs of the donor and acceptor phases, applied voltage, sample flow rate, phosphate content of the acceptor phase, and sample volume, were investigated and optimized. After optimization, the linearity range of 0.5–250.0 µg L
−1
and detection limits of 0.2–1.0 µg L
−1
were obtained for the analytes. The extraction recovery values and preconcentration factors were 10.7–55.3% and 16–83, respectively. The presence of polyaniline in the composition of the nanofibers significantly improved the extraction efficiency of the polar acidic drugs due to providing the possibility of various interactions with the target analytes such as hydrogen bonding, π-stacking, and anion exchange. The obtained results demonstrate the excellent efficiency of the synthesized electrospun nanofibrous mat as a novel support membrane for immobilizing 1-octanol and as an interactive substrate for electromembrane extraction of acidic polar drugs. Eventually, the proposed on-chip EME method exhibits acceptable precision (relative standard deviations less than 9.7% (
n
= 3)) and good accuracy (86–112%) for determining the target analytes in the plasma samples.
Graphical Abstract
In order to study the magnetoelastic instability and natural frequency of a ferromagnetic plate under a magnetic field, different magnetic force models are considered. In the present study, ...considering more realistic assumptions, new equations for the study of the vibrational behavior of ferromagnetic beam plates carrying the electric current in the magnetic field are presented by employing the theory of Eringen and Maxwell relations. Conclusively, the effects of magnetic traction and thermal fields created by electric current and eddy currents are taken into account. The coupled nonlinear differential equations of the system are separated by the Galerkin method and solved numerically. The numerical results are compared with the results in the literature, and the effect of different parameters on the vibration characteristics of the soft ferromagnetic beam plate is investigated. The results show that the components of the force that are created by magnetic tractions, as well as the assumption of thermal couplings, can significantly change the vibrational behavior of the plates. Also, by increasing the intensity of the electric current and the magnetic field, the amplitude of the oscillations of the plate is increased and instability occurs for certain values of these parameters in the system.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
The present study considers the nonlinear vibration behavior of a beam with general boundary conditions that carry an electrical current in the magnetic field. This paper discusses the magnetic ...couple, the transverse magnetic force, the electrical current, and the damper. By contrast, the magnetic field is selected as an arbitrary function of time. Under certain hypotheses, Hamilton's principle is used along with Maxwell's equations to derive the governing equation. An elastically restrained beam carrying an electrical current is also solved using Galerkin's method under a magnetic field. Thus, the effect of the rotational and the translational support flexibilities, the magnetic field, and other parameters are evaluated. For a more detailed investigation, some numerical examples are investigated to present the simplicity and efficiency of this formulation. Based on the numerical results, it is clear that the natural frequency of the ferromagnetic beam is sensitive to the angle and magnetic field. By increasing magnetic field intensity, the magnitude of the natural frequency of the beam increases. But with the increase of the angle, the frequency value decreases. Therefore, at larger angles, the impact of the intensity of the magnetic field will be less. Also, it is determined from the results that the beam deflection in various magnetic fields indicates a significant effect of the boundary conditions, not only on the dynamic response of a damped beam but also on the rate of damping of the response. The dynamic response under the magnetic field is decreased when the beam experiences a stiffer constant in its support. The results are shown that the effect of stiffening for the transitional support is more significant than that of the rotational support. Also, the influence of the boundary constraints becomes smaller when the magnetic field becomes smaller.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, a simple and rapid extraction method based on the application of polypyrrole‐coated Fe3O4 nanoparticles as a magnetic solid‐phase extraction sorbent was successfully developed for the ...extraction and preconcentration of trace amounts of formaldehyde after derivatization with 2,4‐dinitrophenylhydrazine. The analyses were performed by high‐performance liquid chromatography followed by UV detection. Several variables affecting the extraction efficiency of the formaldehyde, i.e., sample pH, amount of sorbent, salt concentration, extraction time and desorption conditions were investigated and optimized. The best working conditions were as follows: sample pH, 5; amount of sorbent, 40 mg; NaCl concentration, 20% w/v; sample volume, 20 mL; extraction time, 12 min; and 100 μL of methanol for desorption of the formaldehyde within 3 min. Under the optimal conditions, the performance of the proposed method was studied in terms of linear dynamic range (10–500 μg/L), correlation coefficient (R2 ≥ 0.998), precision (RSD% ≤ 5.5) and limit of detection (4 μg/L). Finally, the developed method was successfully applied for extraction and determination of formaldehyde in tap, rain and tomato water samples, and satisfactory results were obtained.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Keggin-type aluminum polyoxocation species, Al30, with interesting features resulting from a variety of surface oxygen functional groups, has high adsorption ability of different species so it can be ...served either as nanohybrids or singly in water purification. Insight into surface complex structures of various oxyanions with different activities on Al30 is fundamental for both mechanism and application in wastewater treatment. Reported here is an adsorption behavior investigation of three environmentally problematic oxyanions (phosphate, chromate, and selenate) with different activities on Al30. For this purpose, firstly, Al30 species were consolidated on graphene oxide to use as the sorbent material. Performance of the proposed sorbent evaluated by kinetics and isotherm studies was representative of good agreement of adsorption data with Langmuir isotherm model and pseudo-second-order kinetics for all oxyanions. The underlying molecular binding mechanisms of these oxyanions onto Al30 were revealed by FT-IR spectroscopy, desorption studies, TGA, as well as studying adsorption trends in different pH values. The obtained results boded predominant formation of inner-sphere surface complexes of phosphate and chromate and common contribution of inner- and outer-sphere complexes for selenate, increasing the mobility of selenate. Competitive adsorption studies exhibited a more adsorption affinity and selectivity of Al30 towards phosphate than chromate and selenate, while this was contrary to the result of the single-ion adsorption case, where less adsorption capacity was obtained for phosphate than the other ones.
A new insight into the different interactions as well as affinity of Al30 species towards three environmentally problematic oxyanions Display omitted
•Al30 polyoxocations-modified graphene oxide was applied for fast and efficient uptake of phosphate, chromate and selenate.•Adsorption performance of the sorbent was evaluated by kinetic and isotherm studies.•Results represented different interaction mechanisms (inner- or outer-sphere complex) for phosphate, chromate and selenate.•Comparative study exhibited more affinity of Al30 species towards phosphate than chromate and selenate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The main objective of this study focuses on exploration of the feasibility of Al30 polyoxocations for preparation of a novel sorbent material for a solid-phase extraction (SPE) method by selective ...adsorption and extraction of a class of compounds considering the type of interactions involved in the adsorption process. Accordingly, first Al30 polyoxocations were synthesized and their composite was prepared with graphene oxide (GO) nanosheets as a suitable substrate to be introduced as a SPE sorbent material. Then, the prepared composite was incorporated into polycaprolactone (PCL) nanofibers via electrospinning to present an alternative sorbent for SPE-based on a GO/Al30 nanocomposite (GO/Al30 NC) creating no need for filtering or centrifuging steps. Intercalation of Al30 polyoxocations into the GO layers and the incorporation of GO/Al30 NC into PCL nanofibers was successfully confirmed through FE-SEM, TEM, EDX, XRD, BET, TGA, IR spectroscopy, and zeta potential determination. For investigating the types of probable interactions involved in the adsorption process of different compounds on the proposed sorbents, four statin drugs, cholesterol-lowering agents with various polarity and ionization properties, were selected as model analytes. Factors affecting the extraction efficiency of dispersive SPE and immersed SPE methods using GO/Al30 NC and GO/Al30 NC-PCL nanofibers, respectively, were investigated and optimized. Under optimal conditions, acceptable analytical figures of merit were obtained for both SPE methods. A comparison of extraction efficiencies of the target drugs by the two proposed sorbents, as well as GO nanosheets and PCL nanofibers, was accomplished to study the types of interactions as well as the adsorption mechanism. The results revealed that GO/Al30 NC, having many polar and anion exchange sites caused by Al30 polyoxocations, is a good selective sorbent for acidic polar compounds which their extraction by nonpolar sorbents is not desirable. Additionally, GO/Al30 NC-PCL nanofibers exhibited extraction capability for a wide range of compounds from acidic polar to nonpolar and nonionizable ones.
The applicability of hollow fiber liquid phase microextraction (HF-LPME) for extraction and preconcentration of trace amounts of pioglitazone (PGL) as an anti-diabetic drug in biological fluids, ...prior to determination by high-performance liquid chromatography (HPLC), was evaluated. In this technique, the target drug was extracted into di-
n-hexyl ether immobilized in the wall pores of a porous hollow fiber from 10
mL of the aqueous sample (source phase, SP) with pH 8.0, and then back extracted into the receiving phase (RP) with pH 2.2 located in the lumen of the hollow fiber. The extraction occurred due to a pH gradient between the two sides of the hollow fiber. After extracting for a prescribed time, 24
μL of the RP solution was taken back into the syringe and injected directly into a HPLC instrument for quantification. The Taguchi orthogonal array (OAD) experimental design with an OA
16 (4
5) matrix was employed to optimize the HF-LPME conditions. Different factors affecting the HF-LPME efficiency such as the nature of organic solvent used to impregnate the membrane, pH of the SP and RP, stirring speed, extraction time and ionic strength were studied and optimized. Under the optimum conditions (di-
n-hexyl ether as membrane impregnation solvent, pHs of the SP and RP equal to 8.0 and 2.2, respectively, extraction time of 30
min, stirring speed of 500
rpm and 10% (w/v) NaCl for adjusting the ionic strength), preconcentration factor of 180, linear dynamic range (LDR) of 2.5–250
μg
L
−1 with good correlation of determination (
r
2
>
0.998) and limit of detection (LOD) of 1.0
μg
L
−1 were obtained for the target drug. The percent relative intra-day and inter-day standard deviations (RSDs%) based on five replicate determinations were 4.7 and 15%, respectively. Once LPME was optimized, the performance of the proposed technique was evaluated for the determination of PGL in different types of biological fluids such as plasma and urine samples. The results showed that the proposed HF-LPME method could be successfully applied to determine trace amounts of PGL in biological samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The main objective of this study focuses on exploration of the feasibility of Al30 polyoxocations for preparation of a novel sorbent material for a solid-phase extraction (SPE) method by selective ...adsorption and extraction of a class of compounds considering the type of interactions involved in the adsorption process. Accordingly, first Al30 polyoxocations were synthesized and their composite was prepared with graphene oxide (GO) nanosheets as a suitable substrate to be introduced as a SPE sorbent material. Then, the prepared composite was incorporated into polycaprolactone (PCL) nanofibers via electrospinning to present an alternative sorbent for SPE-based on a GO/Al30 nanocomposite (GO/Al30 NC) creating no need for filtering or centrifuging steps. Intercalation of Al30 polyoxocations into the GO layers and the incorporation of GO/Al30 NC into PCL nanofibers was successfully confirmed through FE-SEM, TEM, EDX, XRD, BET, TGA, IR spectroscopy, and zeta potential determination. For investigating the types of probable interactions involved in the adsorption process of different compounds on the proposed sorbents, four statin drugs, cholesterol-lowering agents with various polarity and ionization properties, were selected as model analytes. Factors affecting the extraction efficiency of dispersive SPE and immersed SPE methods using GO/Al30 NC and GO/Al30 NC-PCL nanofibers, respectively, were investigated and optimized. Under optimal conditions, acceptable analytical figures of merit were obtained for both SPE methods. A comparison of extraction efficiencies of the target drugs by the two proposed sorbents, as well as GO nanosheets and PCL nanofibers, was accomplished to study the types of interactions as well as the adsorption mechanism. The results revealed that GO/Al30 NC, having many polar and anion exchange sites caused by Al30 polyoxocations, is a good selective sorbent for acidic polar compounds which their extraction by nonpolar sorbents is not desirable. Additionally, GO/Al30 NC-PCL nanofibers exhibited extraction capability for a wide range of compounds from acidic polar to nonpolar and nonionizable ones.
Hollow fiber-based liquid phase microextraction (HF-LPME) using conventional solvents is limited by their relative instability and high volatility. The use of supramolecular solvents as a liquid ...membrane phase could overcome these inconveniences due to their negligible vapour pressure and high viscosity. In the present study, a novel and highly flexible method was developed based on supramolecular solvents constructed of vesicles of decanoic acid, which were used for the first time as a solvent in HF-LPME. This solvent is produced from the coacervation of decanoic acid aqueous vesicles by the action of tetrabutylammonium (Bu(4)N(+)). In this work, halogenated anilines as model compounds were extracted from water samples into a supramolecular solvent impregnated in the pores and also filled inside the porous polypropylene hollow fiber membrane. The extracted anilines were separated and determined by high-performance liquid chromatography. The technique requires minimal sample preparation time and toxic organic solvent consumption, and provides a significant advantage over conventional analytical methods. The important parameters influencing the extraction efficiency were studied and optimized utilizing two different optimization methods: one variable at a time and the Box-Behnken design. Under the optimum conditions, the preconcentration factors were in the range of 74 to 203. Linearity of the method was obtained in the range of 1.0-100 μg L(-1) with the correlation coefficients of determination (R(2)) ranging from 0.9901 to 0.9986. The limits of detection for the target anilines were 0.5-1.0 μg L(-1). The relative standard deviations varied from 3.9% to 6.0%. The relative recoveries of the three halogenated anilines from water samples at a spiking level of 20.0 μg L(-1) were in the range of 90.4-107.4%.
•A new polymeric membrane with lewis acid property was developed for the on-chip EME.•The proposed membrane was prepared by electrospinning polycaprolactone and MOF-199.•The EME was applied for ...sulfonamides as polar acidic drugs with Lewis-base property.•Lewis acid-base interaction had an important role in the extraction of sulfonamides.•High extraction efficiency was obtained for sulfonamides with the proposed method.
In this study, a new supporting polymeric membrane having Lewis acid nature was introduced for immobilizing organic solvent in on-chip electromembrane extraction (on-chip EME). For this aim, a polymeric nanofibrous membrane incorporated by a copper based metal-organic framework (MOF-199), with coordinatively unsaturated metal sites and Lewis acid property, was prepared by electrospinning a mixture of polycaprolactone (PCL) and MOF-199. Based on the field emission scanning electron microscopy images, the obtained polymeric membrane consisted of intertwined nanofibers having empty space between the fibers which could provide a suitable place for immobilizing the organic solvent. To demonstrate remarkable extractability of the proposed membrane (PCL/MOF-199 nanofibers) via executing Lewis acid-base interactions, three sulfonamide drugs was selected as anionic polar analytes with Lewis base feature. The parameters affecting the extraction efficiency of the method were optimized through the experimental design method using the orthogonal and rotatable central composite design (CCD). Under optimum conditions, the extraction recoveries ranging from 35.5 to 71.2 %, the relative standard deviations (RSD%) less than 6.45 %, and the detection limits in the range of 0.2–0.5 μg L−1 were achieved. The comparison of the extraction efficiency of the on-chip EME method using the electrospun PCL/MOF-199 nanofibers and PCL nanofibers membranes indicated that the proposed membrane was more efficient for extraction of sulfonamides because of the significant Lewis acid-base interactions of sulfonamides with copper uncoordinated open sites in MOF-199. Finally, the performance of the proposed method for extraction and determination of sulfonamides in three real samples was assayed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
