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.

Heavy metals and organic dyes are the two kinds of main pollutants in the environment and industrial wastewater. The presence of these pollutants in the environmental water can cause serious problems for human health due to their continuous accumulation in living organisms. Hence removing these pollutants from wastewater and environmental water has become a particular issue in recent years and various methods have been extensively studied for this purpose. Recently, electrospun nanofibrous membranes have attracted great attention in terms of application as adsorbent for removing different pollutants such as heavy metals and dyes due to low-cost preparation, fast adsorption rates, high surface area, high adsorption efficiency, and the possibility of their modification. Various methods have been reported to increase the surface area and adsorption capacity as well as the selectivity of these adsorbents towards different species. This chapter focuses on studies related to the different modification processes of electrospun nanofibrous membranes to improve their selectivity and adsorption capacity for different pollutants in water treatment purposes. The classification of electrospun nanofibrous membranes based on their composition and synthesis strategy and their application in water remediation have been reviewed in this study.

Electromembrane extraction (EME), despite its high performance in the extraction of highly polar basic analytes, has challenges in extracting polar acidic compounds. This is the result of a lack of access to the suitable supported liquid membrane (SLM) for this group of analytes. Therefore, it would be valuable to provide a suitable solution for this problem. Accordingly, in the present study, a new method based on on-chip EME followed by HPLC with UV detection was developed for the extraction and determination of some polar acidic drugs in order to provide high extraction efficiency. Here, a new polymeric sheet was introduced as a support for SLM immobilization, which is not only used to impregnate 1-octanol as SLM but also enhances extraction recovery by exerting effective interactions with target acidic analytes. The polymeric sheet was composed of nanofibers prepared by electrospinning polycaprolactone blended with a composite of graphene oxide and aluminum polycations. Encapsulation of the composite in polycaprolactone nanofibers improved the extraction efficiency of polar acidic compounds by creating additional interactions with the target analytes, including hydrogen bonding, dipole- dipole, π-π stacking, and anion exchange process. The electrospun nanofiber-based sheet was characterized by FE-SEM, EDX, elemental mapping, TEM, and AFM. The extraction parameters were further optimized with an orthogonal-rotatable central composite design (CCD). Applying CCD determined optimal conditions by minimum experiments, and interactions between the parameters were clarified. Under optimized conditions, the proposed method provided extraction recoveries from 36.5 to 64.1%, relative standard deviations less than 5.7% (n = 4), and detection limits of 0.3–0.5 μg L−1. Furthermore, the proposed method was successfully used for the determination of target analytes in plasma samples, providing good accuracy (87–110%) and precision (3.2–8.8%).

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.

The present study investigates the synthesis and application of the graphene oxide-alumina nanocomposite as a new adsorbent for the dispersive solid-phase extraction of three parabens and their determination using high-performance liquid chromatography-ultraviolet detection. The characterization of the synthesized material was accomplished and its size, morphology, chemical composition, porosity, and thermal stability were studied. Application of the proposed strategy for the synthesis of the nanocomposite resulted in the incorporation of Al2O3 nanoparticles into graphene oxide nanosheets, further resulting in the exfoliation of graphene oxide nanosheets increasing their surface area. An orthogonal rotatable central composite design was used to optimize the extraction. Under the optimum conditions, the analytical performance of the method showed a suitable linear dynamic range (0.2–100.0 μg/L), reasonable limits of detection (0.03–0.05 μg/L), and preconcentration factors ranging from 128 to 173. Finally, the new validated method was applied for the determination of parabens in some real samples including wastewater, cream, toothpaste, and juice samples with satisfactory recoveries (88%– 109%), and relative standard deviations less than 8.7% (n = 3). Results demonstrated that inserting alumina nanoparticles into graphene oxide nanosheets improved the extraction efficiency of parabens, as polar acidic compounds, by providing additional efficient interactions including hydrogen bonding, dipole-dipole, and Brønsted and Lewis acid-base interactions.

Employing simple precipitation (fractionation) using Cohn method and weak anion exchange chromatography with DEAE resin, antibodies such as Immunoglobulin G are purified from human plasma. Fractions are eluted from column in four different regions depending on washing NaCl concentrations. Absorbance and excitation-emission fluorescence spectral data are measured for separated chromatographic fractions and analyzed using Multivariate Curve Resolution- Alternating Least Squares (MCR-ALS) and Parallel Factor Analysis (PARAFAC) techniques. Resolved concentration and spectral profiles provided information about existing components in each fraction. Protein and non-protein components are distinguished considering their resolved pure spectra and information from the two applied spectroscopic techniques is complementary. A number of components displayed both fluorescence and absorbance signals. When concentration of component (protein or non-protein) in sample is low and no significant absorbance signal is observed, sensitive fluorescence is useful to recognize the component and for non-fluorescent components absorbance spectra are utilized. Electrophoresis is utilized for separation of proteins in each fraction and showed that one distinguished protein from fluorescence and/or absorbance data can be a group of proteins with similar pure spectra and retention volume. Results showed presence of two protein in the first region (IgM and IgA), a group of proteins in second region (IgM, α-globulin, and IgG), a pure protein in third region (IgG), and a group of β-globulin proteins in fifth region. It is well and clearly shown that multivariate analysis of different data sets with complementary information is necessary for better interpretation of such technically simple and biochemically complicated systems.

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.

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.

Evaluating the relationship between structure and function of metal–organic frameworks (MOFs) is an interesting issue that is discussed in this work. Here, four isoreticular 3D porous zinc(II) MOFs with pcu topology, including [Zn(oba)(4-bpmb)0.5]·(DMF)1.5 (TMU-6), [Zn(oba)(bpmn)0.5]·(DMF)1.5 (TMU-21), [Zn2(oba)2(bpfb)]·(DMF)5 (TMU-23) and [Zn2(oba)2(bpfn)]·(DMF)2 (TMU-24), H2oba = 4,4′-oxybisbenzoic acid, bpmb = N,N′-bis-(4-pyridylmethylene)-1,4-benzenediamine, bpmn = N,N′-bis-(4-pyridylmethylene)-1,5-naphthalenediamine, bpfb = N,N′-bis-(4-pyridylformamide)-1,4-benzenediamine and bpfn = N,N′-bis(4-pyridylformamide)-1,5-naphthalenediamine, containing imine- (TMU-6 and TMU-21) and amide- (TMU-23 and TMU-24) decorated pores, were successfully synthesized by a mechanochemical method. Then, adsorption efficiency of these four MOFs for some heavy metal ions was studied to evaluate effects of the types of functional groups of the pillars in different MOFs on the adsorption process. The results indicated that amide-decorated MOFs show a better adsorption efficiency toward metal ions than the imine-decorated MOFs. In the following, TMU-23 was used as an efficient sorbent for extraction and removal of some heavy metal ions (Co2+, Cd2+, Cu2+, Cr3+, Fe2+, and Pb2+) and its analytical performance was evaluated and determined. In addition, DFT calculations were performed on possible coordination modes between cations and simplified functional groups of the related pillars in each MOF and a probable interaction mechanism of the MOFs and the metal ions was evaluated.

In this study, a magnetic infinite coordination polymer with the morphology of nanocapsule, as an efficient adsorbent for removal of Hg2+ ions has been introduced. This infinite coordination polymer was synthesized from Zn2+ ion and a ditopic organic ligand (1,3-bis(tetrazol-5-ylmethyl)benzene (btb)) and its efficiency as an adsorbent was studied in view of adsorption isotherms, kinetics and thermodynamics. The adsorption capacity of mercury(II) ions was impressed by pH value and adsorption time and the optimal adsorption conditions were pH value of 8, adsorption time of 75 min. The adsorption isotherm was analyzed by Freundlich and Langmuir equations and was fitted with Langmuir model better. Outcomes indicated that the adsorption was an endothermic process. Moreover, this adsorption process was fitted with pseudo-second order model kinetically. Finally, the magnetic properties of nanocapsules synthesized in high and low concentration of initial reagents were investigated. Studies showed that the saturation magnetization of nanocapsules synthesized in low concentration of initial reagent is higher.

Six new NiCr layered double hydroxides (LDHs) intercalated with different inter-layer anions, including diphenylamine-4-sulfonate (DPA), dodecyl sulfonate (DS), pentansulfonate (PS), terephthalate (TA), fumarate (FA) and 2-ethylhexyl hydrogenphosphate (EHP), were synthesized and used to removal of Cd2+, Pb2+, Cu2+, and Zn2+ ions from water samples. The maximum adsorption capacities (qm) for the mentioned LDHs based on their inter-layer anions were DPA > DS > PS > TA > FA > DEHP. This observation highlights the key role of the structure of the inter-layer anions in the adsorption behavior of LDHs. The sulfonate-based LDHs showed better adsorption efficiency than carboxylate-based LDHs, and phosphonate-based LDHs showed the lowest adsorption efficiency. Also, at both high and low concentrations of the metal ions, the length of R– groups and the type of functional groups of inter-layer anions play a key role in the adsorption process. Subsequently, DPA-LDH, due to having the highest qm value among intercalated-LDHs, was chosen as an efficient sorbent for the removal of the metal ions from aqueous samples and its selectivity for adsorption of metal ions was investigated. DPA-LDH displayed a selectivity order of Zn2+ < Cu2+ <<< Cd2+ < Pb2+ for their adsorption, providing good separation of much more toxic metal ions of Cd2+ and Pb2+ from Zn2+ and Cu2+. For the highly toxic Pb2+ and Cd2+, enormous qm values as large as 479 and 282 mg g−1 can be obtained, respectively; and these are among the highest qm values reported for Pb2+ and Cd2+ sorbents. The very high distribution coefficient (Kd) values for Pb2+ (1.99 × 108 mL g−1) and Cd2+ (1.99 × 107 mL g−1), obtained using a V/m ratio of 2000 mL g−1, place the DPA-LDH at the top of materials known for such removal.

Synthesis of new porous materials has been developed for efficient capture of pollutants in environmental sciences. Here, the application of a new metal–organic framework (TMU-30) has been reported based on isonicotinate N-oxide as an adsorptive site for fast and highly efficient aqueous phase adsorption of Cr(VI). The adsorption process showed no remarkable effect over a pH range of 2–9. The maximum capacity of the adsorption was reached in just less than 10 min and followed the pseudo-second-order kinetics. The maximum capacity of 2.86 mol mol–1 (145 mg/g) was obtained according to Langmuir model at 298 K. The spontaneous adsorption and an endothermic process were controlled by positive entropy changes. XPS analysis revealed electrostatic interactions between N-oxide groups of TMU-30 and Cr(VI) species, which were responsible for the adsorption process.

A solid-phase extraction (SPE) sorbent, a Zn(II) based metal–organic framework, was prepared via a simple, solventless, green and a low-cost mechanosynthesis process. This sorbent was applied to the extraction of three plasticizer compounds (Di-n-butyl phthalate (DBP), di-2-(ethylhexyl) phthalate (DEHP) and dioctyladipate(DOA)) prior to analysis by gas chromatography with a flame ionization detector (GC-FID). The applied sorbent had the advantages of large surface area, simple and low cost preparation process and good stability. Analytical performances of the proposed method were investigated under the optimum extraction conditions and compared with other SPE methods reported for the same analytes. Validation experiments showed that the optimized method presents good linearity (R2 > 0.994), satisfactory precision (RSD ≤ 6.3%), and suitable pre-concentration factors (92–295). The results indicated that solid phase extraction with the proposed sorbent had advantages of convenience, good sensitivity, high efficiency, and it could also be applied successfully to analyze plasticizers in real water samples.

Magnetite (Fe3O4) nanoparticles were coated with tannic acid to give nanoparticles (NPs) of the type Fe3O4@TA and are shown to be a viable sorbent for preconcentration of Cd2+, Co2+ and Cr3+. The size, morphology, composition, and properties of the Fe3O4@TA NPs were characterized by field emission scanning electron microscopy, energy-dispersive X-ray analysis, vibrating sample magnetometery and FTIR. They were applied to the solid-phase extraction of the metal ions from environmental water samples prior to their quantitation by flow injection inductively coupled plasma-optical emission spectrometry. The effects of sample solution, extraction and desorption times, kind of eluent and quantity of sorbent were optimized. The calibration plots are linear in the concentration ranges from 0.5 to 100 μg L−1 (for both Cd and Co) and from 0.2 to 100 μg L−1 (for Cr). The limits of detection are between 0.1 and 0.2 μg L−1. The intra-day relative standard deviations based on four replicates are in the range of 6.1 to 7.1 %. The method was successfully applied to the determination of the three metal ions in (spiked) tap water, mineral water, and river water. Recoveries varied in the range from 90 to 109 %, this confirming the good performance of the method.

We describe a method for the microextraction of the four model triazine herbicides cyanazine, simazine, prometon and propazine from water samples. It is based on the use of the supramolecular solvent decanoic acid and magnetic nanoparticles (NPs) which are applied to magnetically separate the decanoic acid micelles containing the extracted herbicides. Following desorption of the coating from the magnetic NPs with methanol, the solution was submitted to HPLC with UV detection. The pH values, amount of decanoic acid and sorbent, sample temperature, stirring rate, salt addition, and extraction time were optimized. Under optimal conditions, the preconcentration factors and relative recoveries for the four herbicides range from 183 to 256 and from 90.3 to 105.0 %, respectively. The analytical ranges extend from 0.3 to 250 μg∙mL‾1, and the limits of detection (LODs) are between 0.3 and 0.5 μg∙mL‾1 (based on an S/N ratio of 3). The precision of the method, expressed as relative standard deviation for extraction and determination of the 100 μg∙mL‾1 analytes in the samples solution is in the range from 4.6 to 6.5 %. We also critically compare the present method with various others.

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.

The potential of polypyrrole-coated Fe3O4 nanoparticles (Fe3O4@PPy NPs) for removal of two anionic dyes from aqueous solutions was studied. The dye removal process was affected by several parameters such as pH, sorbent amount, and contact time, and were optimized using the response surface methodology (RSM) based on orthogonal central composite design (OCCD). The maximum removal of dyes was achieved at the adsorbent amount of 0.1–0.12 g/100 mL at pH 4–5.4 in 60 min. Three kinetic models; namely, pseudo-first-order, pseudo-second-order, and intra-particle diffusion were used to analyze the adsorption mechanism. The kinetic results showed that the pseudo-second-order equation was the best model. The isotherm analysis indicated that the equilibrium data were well fitted to the Langmuir isotherm model, showing a monolayer adsorption manner of the dyes onto a homogeneous surface of the modified nanoparticles. According to the experimental results, about 97.8% of alizarin yellow and 78.7% of alizarin red were removed from aqueous solutions under optimal conditions. The maximum adsorption capacities for alizarin red-S and alizarin yellow GG in the concentration ranges studied were 116.3 and 113.6 mg g−1, respectively, which were higher than the recent reports for potential adsorbents in the literature. The results obtained showed that the Fe3O4@PPy NPs are an appropriate adsorbent for removal of anionic dyes from aqueous solutions.

The three zinc(II) metal–organic frameworks [Zn2(oba)2(4-bpdb)]·(DMF)x (TMU-4), [Zn(oba)(4-bpdh)0.5]n·(DMF)y (TMU-5), and [Zn(oba)(4-bpmb)0.5]n·(DMF)z (TMU-6) [DMF = dimethylformamide, H2oba = 4,4′-oxybisbenzoic acid, 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene, and 4-bpmb = N1,N4-bis((pyridin-4-yl)methylene)benzene-1,4-diamine], which contain azine-functionalized pores, have been successfully synthesized by mechanosynthesis as a convenient, rapid, low-cost, solventless, and green process. These MOFs were studied for the removal and extraction of some heavy-metal ions from aqueous samples, and the effects of the basicity and void space of these MOFs on adsorption efficiency were evaluated. The results showed that, for trace amounts of metal ions, the basicity of the N-donor ligands in the MOFs determines the adsorption efficiency of the MOFs for the metal ions. In contrast, at high concentrations of metal ions, the void space of the MOFs plays a main role in the adsorption process. The studies conducted revealed that, among the three MOFs, TMU-6 had a lower adsorption efficiency for metal ions than the other two MOFs. This result can be attributed to the greater basicity of the azine groups on the TMU-4 and TMU-5 pore walls as compared to the imine groups on the N-donor ligands on the TMU-6 pore walls. Subsequently, TMU-5 was chosen as an efficient sorbent for the extraction and preconcentration of trace amounts of some heavy-metal ions including Cd(II), Co(II), Cr(III), Cu(II), and Pb(II), followed by their determination by flow injection inductively coupled plasma optical emission spectrometry. Several variables affecting the extraction efficiency of the analytes were investigated and optimized. The optimized methodology exhibits a good linearity between 0.05 and 100 μg L–1 (R2 > 0.9935) and detection limits in the range of 0.01–1.0 μg L–1. The method has enhancement factors between 42 and 225 and relative standard deviations (RSDs) of 2.9–6.2%. Subsequently, the potential applicability of the proposed method was evaluated for the extraction and determination of target metal ions in some environmental water samples.

A rapid, simple and efficient procedure is demonstrated for extraction and determination of an endocrine-disrupting compound, synthetic estrogen, 17α-ethynylestradiol (EE2), in water and wastewater samples via magnetic solid-phase extraction followed by high-performance liquid chromatography coupled with UV detection. The analytical method is based on extraction of EE2 by dispersing magnetic nanoparticles in sample solution for a desired time and then eluting the analytes with an appropriate solvent. The nanoparticles were modified with a hydrophobic material by self-assembling an organosulfur compound (bis-(2,4,4-trimethylpentyl)-dithiophosphinic acid) onto the silver-coated Fe3O4 nanoparticles as sorbent. The effects of several parameters, such as amount of sorbent, sample volume, extraction time, ionic strength and desorption conditions, were examined to obtain better efficiency. The optimized methodology exhibited a good linearity between 0.5 and 100 μg L−1 with a limit of detection (LOD) of 0.3 μg L−1, and a preconcentration factor of 245 with intra- and inter-day precisions (relative standard deviations) 2.4 and 3.2 %, respectively. The developed method was successfully applied for extraction and determination of EE2 in different real water samples including river water, surface water and influent and effluent of a wastewater treatment plant, and satisfactory results were achieved. The method, which provides a good preconcentration factor, a low LOD and low consumption of the organic solvent, presents a rapid, simple and efficient procedure for determining EE2 in aqueous samples.

Electromembrane surrounded solid phase microextraction (EM-SPME) of acidic herbicides was studied for the first time. In order to investigate the capability of this new microextraction technique to analyze acidic targets, chlorophenoxy acid (CPA) herbicides were quantified in plant tissue. 1-Octanol, was sustained in the pores of the wall of a hollow fiber and served as supported liquid membrane (SLM). Other EM-SPME related parameters, including extraction time, applied voltage, and pHs of the sample solution and the acceptor phase, were optimized using experimental design. A 20 min time frame was needed to reach the highest extraction efficiency of the analytes from a 24 mL alkaline sample solution across the organic liquid membrane and into the aqueous acceptor phase through a 50 V electrical field, and to their final adsorption on a carbonaceous anode. In addition to high sample cleanup, which made the proposed method appropriate for analysis of acidic compounds in a complicated media (plant tissue), 4.8% of 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 0.6% of 2,4-dichlorophenoxyacetic acid (2,4-D) were adsorbed on the anode, resulting in suitable detection limits (less than 5 ng mL–1), and admissible repeatability and reproducibility (intra- and interassay precision were in the ranges of 5.2–8.5% and 8.8–12.0%, respectively). Linearity of the method was scrutinized within the ranges of 1.0–500.0 and 10.0–500.0 ng mL–1 for MCPA and 2,4-D, respectively, and coefficients of determination greater than 0.9958 were obtained. Optimal conditions of EM-SPME of the herbicides were employed for analysis of CPAs in whole wheat tissue.

We have developed a fast method for sensitive extraction and determination of the metal ions silver(I), gold(III), copper(II) and palladium(II). Fe3O4 magnetic nanoparticles were modified with polythiophene and used for extraction the metal ions without a chelating agent. Following extraction, the ions were determined by flow injection inductively coupled plasma optical emission spectrometry. The influence of sample pH, type and volume of eluent, amount of adsorbent, sample volume and time of adsorption and desorption were optimized. Under the optimum conditions, the calibration plots are linear in the 0.75 to 100 μg L−1 concentration range (R2 > 0.998), limits of detection in the range from 0.2 to 2.0 μg L−1, and enhancement factors in the range from 70 to 129. Precisions, expressed as relative standard deviations, are lower than 4.2 %. The applicability of the method was demonstrated by the successful analysis of tap water, mineral water, and river water.

In this research, the applicability of polypyrrole-coated Fe3O4 nanoparticles (Fe3O4@PPy NPs) as an anion exchange magnetic nanosorbent is demonstrated. For this purpose, three nitrophenols were selected as models which are acidic compounds with low log P values and their extraction in neutral form (only based on hydrophobic interactions) is difficult. The extracted nitrophenols were separated and determined by high-performance liquid chromatography-UV detection. The size, morphology and surface coating of synthesized Fe3O4@PPy NPs have been characterized via different techniques such as Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and thermo-gravimetric analysis. The important parameters influencing the extraction efficiency were studied and optimized. Under the optimum extraction conditions (300 mL sample solution with pH 10, extraction and desorption times of 10 and 2 min, respectively, 500 μL of 0.1 M HNO3 in acetonitrile as eluent, and 40 mg of adsorbent), a linear range between 0.75 and 100 μg L−1 (R2 > 0.997), and limits of detection ranging from 0.3 to 0.4 μg L−1 were obtained. Preconcentration factors in the range of 125–180 were achieved and relative standard deviations (RSDs%) were less than 4.9 (n = 4) for the three nitrophenols. The analytical method was successfully applied for environmental water samples such as tap water, rain water and river water. The recoveries varied within the range of 84–109% confirming good performance of the method in various waters samples. The results showed that the proposed method is a rapid, convenient and feasible technique for determination of nitrophenols in aqueous samples.

In the present work, a novel type of superparamagnetic nanosorbent, polythiophene-coated Fe3O4 nanoparticles (Fe3O4@PTh NPs), have been successfully synthesized. The synthesized NPs were characterized by scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy, and thermal gravimetric analysis (TGA). The synthesized Fe3O4@PTh NPs were applied as an efficient sorbent for extraction and preconcentration of several typical plasticizer compounds (di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), and dioctyl adipate (DOA)) from environmental water samples. Separation of Fe3O4@PTh NPs from the aqueous solution was simply achieved by applying external magnetic field. Separation and determination of the extracted plasticizers was performed by gas chromatography–flame ionization detection (GC–FID). Several variables affecting the extraction efficiency of the analytes i.e., amount of NPs sorbent, salt concentration, extraction time, and desorption conditions were investigated and optimized. The best working conditions were as follows: amount of sorbent, 100 mg; NaCl concentration, 30% (w/v); sample volume, 45 mL; extraction time, 10 min; and 100 μL of ethyl acetate for desorption of the analytes within 2 min. Under optimized conditions, preconcentration factors for DBP, DEHP, and DOA were obtained as 86, 194, and 213, respectively. The calibration curves were linear (R2 > 0.998) in the concentration range of 0.4–100 μg L−1 for both DEHP and DOA and 0.7–100 μg L−1 for DBP. The limits of detection (LODs) were obtained in the range of 0.2–0.4 μg L−1. The intra-day relative standard deviations (RSDs%) based on four replicates were obtained in the range of 4.0–12.3%. The proposed procedure was applied to analysis of water samples including river water, bottled mineral water, and boiling water exposed to polyethylene container (after cooling) and recoveries between 85 and 99% and RSDs lower than 12.8% were obtained.

A novel sorbent for magnetic solid-phase extraction by self-assembling of organosulfur compound, (bis-(2,4,4-trimethylpentyl)-dithiophosphinic acid), onto the silver-coated Fe3O4 nanoparticles was introduced. Due to the formation of covalent bond of SsinglebondAg, the new coating on the silver surface was very stable and showed high thermal stability (up to 320 °C). The size, morphology, composition, and properties of the prepared nanoparticles have also been characterized and determined using scanning electron microscopy (SEM), energy-dispersive X-ray analyzer (EDX), dynamic light scattering (DLS), Fourier transform-infrared (FT-IR) spectroscopy, and thermal gravimetric analysis (TGA). Extraction efficiency of the new sorbent was investigated by extraction of five polycyclic aromatic hydrocarbons (PAHs) as model compounds. The optimum extraction conditions for PAHs were obtained as of extraction time, 20 min; 50 mg sorbent from 100 mL of the sample solution, and elution with 100 μL of 1-propanol under fierce vortex for 2 min. Under the optimal conditions, the calibration curves were obtained in the range of 0.05–100 μg L−1 (R2 > 0.9980) and the LODs (S/N = 3) were obtained in the range of 0.02–0.10 μg L−1. Relative standard deviations (RSDs) for intra- and inter-day precision were 2.6–4.2% and 3.6–8.3%, respectively. In addition, feasibility of the method was demonstrated with extraction and determination of PAHs from some real samples containing tap water, hookah water as well as soil samples with relative recovery of 82.4–109.0% and RSDs of 3.5–11.6%.

In this study, the capability of the prepared polyaniline-coated Fe3O4 nanoparticles for magnetic solid-phase extraction of three parabens from environmental wastewater, cream, and toothpaste samples is presented. Synthesized Fe3O4 nanoparticles were coated with sulfate-doped polyaniline via polymerization of aniline in the presence of Fe3O4 nanoparticles and sulfuric acid. Here, polyaniline-coated Fe3O4 nanoparticles are presented as anion exchange sorbent, which extract anionic form of parabens via anion exchange with dopant of polyaniline. The experimental conditions affecting extraction efficiency were further studied and optimized. The experimental results showed that maximum extraction efficiency can be obtained at 70 mL sample solution of pH 8, extraction and desorption times of 2 and 1 min, respectively, 100 μL of 3% (v/v) acetic acid in acetonitrile as eluent, and 100 mg of the adsorbent. Under these conditions, the linear dynamic ranges were 0.5–100 μg/L with good correlation coefficients (0.998–0.999). The detection limits were in the range of 0.3–0.4 μg/L and the relative standard deviations were less than 2.4 (n = 5) for the three parabens. Finally, this fast and efficient method was further employed for determination of target analytes in cream, toothpaste, and environmental wastewater samples and satisfactory results were obtained.

In the present study, a novel quantitative method, namely magnetic nanoparticle-based solid-phase extraction (MSPE), was applied to extract vitamin B12 from pharmaceutical formulations. The technique involves the use of Fe3O4 nanoparticles modified by sodium dodecyl sulfate (SDS) as an efficient adsorbent for solid-phase extraction of vitamin B12. Collection of magnetic nanoparticles (MNPs) from aqueous solution was simply achieved by applying external magnetic field. The analyte was desorbed from MNPs using alkali 1-propanol. The extracted analyte was analyzed by using flow injection inductively coupled plasma–optical emission spectrometry. Factors affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, enhancement factor of 184, linear dynamic range of 2.5–500 μg L−1 with correlation of determination (R 2 > 0.999), and limit of detection of 1.0 μg L−1 were obtained for vitamin B12. The percent relative standard deviation based on five-replicate determination was less than 6.2%. The method was successfully applied for extraction and determination of vitamin B12 in different types of pharmaceutical samples such as multivitamin tablet, effervescent tablet, and injection sample. The results showed that the proposed method based on SDS–Fe3O4 MSPE was a simple, accurate, and highly efficient approach for analysis of vitamin B12.

A novel method for the determination of palladium as a metal ion model was developed by ion pair based surfactant-assisted microextraction (IP-SAME) and inductively coupled plasma-optical detection (ICP-OES). In this methodology, a cationic surfactant was used in extraction process. It has two fundamental functions: (1) the formation of an emulsified phase and (2) the ion pair formation with Pd(II) in the presence of iodide ions and making extractable into organic phase (active microextraction). The effective parameters on the extraction recovery such as the types of extraction solvent and the surfactant, surfactant concentration, KI amount and HCl concentration of the sample were investigated and optimized. In the proposed approach, tetradecyl trimethyl ammonium bromide (TTAB) was used as emulsifier and ion pairing agent, and 1-octanol was selected as extraction solvent. Under the optimum conditions, the enhancement factor as large as 146 was obtained. The detection limit for palladium was 0.2 μg L−1, and the relative standard deviation (RSD) was 4.1% (n = 5, C = 10.0 μg L−1). The proposed method was applied for extraction and determination of palladium in different water samples.

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 (Bu4N+). 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 (R2) 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%.

The utilization of modified magnetite nanoparticles (Fe3O4 NPs) with a cationic surfactant (cetyltrimethylammonium bromide (CTAB)) as an efficient adsorbent was successfully carried out to remove reactive black 5 (RBBA), reactive red 198 (RRR) and reactive blue 21 (RTB) dyes from aqueous solutions. First, a reactor was designed to be simple, repeatable and efficient in its synthesis of Fe3O4 NPs via co-precipitation method. Then, an orthogonal array design (OAD), four factor-four level (44) matrix was applied to assign affecting factors on removing of the dyes from aqueous solutions. The obtained results from ANOVA showed that the amount of CTAB and NaCl% significantly affect the adsorption of RBBA, RRR and RTB dyes. The sorption kinetics of the dyes were best described by a second-order kinetic model, suggesting chemisorptions mechanism. Also, dye adsorption equilibrium state data were fitted well to the Langmuir isotherm rather than Freundlich isotherm. Also, the maximum monolayer capacity, qmax, obtained from the Langmuir was 312.5, 163.9 and 556.2 mg g-1 for RBBA, RRR and RTB, respectively. The obtained results in the present study indicated that the CTAB-coated Fe3O4 NPs can be an efficient adsorbent material for removal of reactive dyes form aqueous solutions.

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 OA16 (45) 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 (r2 > 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.