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The main objective of this study is to predict both the subharmonic and superharmonic resonances of the nonlinear oscillation of nanobeams in the presence of surface free energy effects. To this purpose, Gurtin–Murdoch elasticity theory is adopted to the classical beam theory in order to consider the surface Lame constants, surface mass density, and residual surface stress within the differential equations of motion. The Galerkin method together with the method of multiple scales is utilized to investigate the size-dependent response of nanobeams under hard excitations corresponding to various boundary conditions. A parametric analysis is carried out to indicate the influence of the surface elastic parameters on the frequency-response as well as amplitude-response of the nonlinear secondary resonance including multiple vibration modes and interactions between them. It is seen that for the superharmonic excitation, except for the clamped–free boundary condition, the jump phenomenon is along the hardening direction, while in the clamped–free end supports, it is along the softening direction. Moreover, it is revealed that for the subharmonic excitation, within a specific range of the excitation amplitude, the nanobeam is excited, and this range shifts to lower external force by incorporating the surface free energy effects. It is found that in the case of superharmonic excitation, the value of the excitation frequency associated with the bifurcation point at the peak of the frequency-response curve increases by taking the surface free energy effect into consideration.

Owing to their atomic thickness and low bending rigidity, suspended two-dimensional (2D) materials are prone to wrinkle formation. Here, we use molecular dynamics (MD) simulations to probe the effect of these wrinkles on the nonlinear elasticity of atomically thin graphene membranes. We observe a stress-strain response that consists of two linear regions that are separated by a transition. It is found that this transition is sharp in membranes where wrinkles are formed by uneven stresses at the boundaries. However, when wrinkles are formed by crystal defects, this nonlinear transition is seen to be more gradual. To capture these effects, we use a phenomenological model based on experimentally measurable quantities. We demonstrate the model's fidelity by fitting it to the MD simulated nonlinear response of many graphene membranes providing evidence that the sharpness of the transition between the linear regions in the stress-strain response is a measure of the type of wrinkles and can be quantified by our model.

A vortex assisted dispersive solid phase extraction approach (VADSPE) based on crab shell powder as biodegradable and biocompatible μ-sorbent was developed for simultaneous analysis of three benzodiazepines (BZPs): Oxazepam, Flurazepamand Diazepam, in biological matrixes included blood, nail, hair and urine samples. The effective parameters in VADSPE process, including the volume of uptake solvent, the dosage of sorbent, extraction time and back extraction time, were optimized using response surface methodology(RSM) based on central composite design(CCD). The suggested technique allows successful trapping of BZPs in a single-step extraction. Under the optimized extraction conditions, the proposed approach was exhibited low limits of detection (0.003–1.2 μg·mL−1), an acceptable linearity (0.04–20 μg·mL−1). Method performance was assessed by recovery experiments at spiking levels of 10 μg·mL−1(n = 5) for BZPs in blood, nail, hair and urine samples. Relative recoveries were determined by HPLC, which were between 36%and 95.6%.

We describe a magnetic nanocomposite that consists of Fe3O4/carbon nanosphere/polypyrrole (Fe3O4/CNS/PPy). The synthesized nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. The nanocomposite was successfully applied to extract of the polycyclic aromatic hydrocarbons (PAHs) from water samples. Compared to Fe3O4/PPy, the Fe3O4/CNS/PPy nanocomposite exhibits improved properties in terms of extraction. The amount of adsorbent, salt effect, extraction time, desorption time, type, and the volume of desorption solvent were optimized. Following the desorption of the extracted analytes, the PAHs (i.e., naphthalene, 2-methylnaphthalene, 2-bromonaphthalene, fluorene, and anthracene) were quantified by gas chromatography–flame ionization detector. The PAHs can be determined in 0.05–100.00 ng mL−1 concentration range, with limits of detection (at an S/N ratio of 3) ranging from 0.01 to 0.05 ng mL−1. The repeatability of the method was investigated with relative standard deviations of lower than 9.9% (n = 5). Also, the recoveries from spiked real water samples were in the range of 88.9–99.0%. The results indicate that the novel material can be successfully applied for the extraction and analysis of PAHs from water samples.

The aim of this research was to develop a low price adsorbent with the abundant of source to remove manganese and cobalt from water samples. Tea waste solid-phase extraction coupled with flame atomic absorption spectrometry (FAAS) was used for the extraction and determination of manganese and cobalt ions. Response surface methodology (RSM) and hybrid of artificial neural network-particle swarm optimization (ANN-PSO) have been used to develop predictive models for simulation and optimization of tea waste extraction process. The pH, amount of tea waste, concentration of PAN (complexing agent), eluent volume, concentration of eluent, and sample and eluent flow rates were the input variables, while the extraction percent of Mn and Co were the output. Two approaches for their modeling and optimization capabilities were compared. The generalization and predictive capabilities of both RSM and ANN were compared by unseen data. The results have shown the superiority of ANN compared to RSM. Under the optimum conditions, the detection limits of Mn and Co were 0.5 and 0.67 μg L −1 , respectively. This method was applied to the preconcentration and determination of manganese and cobalt from water samples.

A simple, rapid, highly efficient, and reliable sample preparation method has been developed for the extraction and analysis of triazole pesticides from cucumber, lettuce, bell pepper, cabbage, and tomato samples. This new sorbent in the hollow-fiber solid-phase microextraction method is based on the synthesis of polyethylene glycol-polyethylene glycol grafted flower-like cupric oxide nanoparticles using sol-gel technology. Afterward, the analytes were analyzed by high-performance liquid chromatography with ultraviolet detection. The main parameters that affect microextraction efficiency were evaluated and optimized. This method has afforded good linearity ranges (0.5-50 000 ng/mL for hexaconazol, 0.012-50 000 ng/mL for penconazol, and 0.02-50 000 ng/mL for diniconazol), adequate precision (2.9-6.17%, n = 3), batch-to-batch reproducibility (4.33-8.12%), and low instrumental LODs between 0.003 and 0.097 ng/mL (n = 8). Recoveries and enrichment factors were 85.46-97.47 and 751-1312%, respectively.

A magnetic solid-phase extraction method coupled with gas chromatography was proposed for the determination of polycyclic aromatic hydrocarbons in the environmental water samples. The magnetic adsorbent was prepared by incorporating Fe3 O4 nanoparticles, multi-walled carbon nanotubes, and polypyrrole. The main factors affecting the extraction efficiency including the amount of the sorbents, desorption conditions, extraction time, salt concentration, and sample solution pH were investigated and optimized. Under the optimum conditions, good linearity was obtained within the range of 0.03-100 ng/mL for all analytes, with correlation coefficients ranging from 0.9942 to 0.9973. The method detection limits (S/N = 3) were in the range of 0.01-0.04 ng/mL and the limits of quantification (S/N = 10) were 0.03-0.1 ng/mL. Repeatability of the method was assessed through five consecutive extractions of independently prepared solutions at concentrations of 0.1, 10, and 100 ng/mL of the compounds. The observed repeatability ranged 3.4-10.9% depending of the compound considered. The proposed method was successfully applied in the analysis of PAHs in environmental samples (tap, well, river, and wastewater). The recoveries of the method ranged between 93.4 and 99.0%. The procedure proved to be efficient and environmentally friendly.

A headspace solid-phase microextraction (HS-SPME) method was developed for isolation of monocyclic aromatic amines from water samples followed by gas chromatography–flame ionization detector (GC–FID). In this work, the effect of the presence of ionic liquid (namely, 1-hexyl-3-methyl-imidazolium hexafluorophosphate [C6MIM][PF6]) was investigated in the sol–gel coating solutions on the morphology and extraction behavior of the resulting hybrid organic–inorganic sol–gel sorbents utilized in SPME. Hydroxy-terminated poly(dimethylsiloxane) (PDMS) was used as the sol–gel active organic component for sol–gel hybrid coatings. Two different coated fibers that were prepared are PDMS and PDMS-IL ([C6MIM][PF6]) fibers. Under the optimal conditions, the method detection limits (S/N = 3) with PDMS-IL were in the range of 0.001–0.1 ng/mL and the limits of quantification (S/N = 10) between 0.005 and 0.5 ng/mL. The relative standard deviations for one fiber (n = 5) were obtained from 3.1 up to 8.5% and between fibers or batch to batch (n = 3) in the range of 5.3–10.1%. The developed method was successfully applied to real water and juice fruits samples while the relative recovery percentages obtained for the spiked water samples at 0.1 ng/mL were from 83.3 to 95.0%.

This work demonstrates the use of montmorillonite (MMT) clay minerals as an effective and low cost catalyst support for Pt nanoparticles for electrocatalytic oxidation of ethanol molecules. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray (EDX) spectroscopy were employed for the morphological study of the modified catalyst layers. The SEM images indicate that the platinum nanoparticles are dispersed in a homogeneous arrangement on a MMT matrix and the EDX spectrum confirms the presence of the Pt element. The results obtained from cyclic voltammetry measurements show that the FTO/MMT/Pt electrode is catalytically more active for electrooxidation of ethanol molecules than the FTO/Pt electrode. The electrochemical impedance spectroscopy (EIS) analysis and chronoamperometric measurements confirmed this result and the Tafel plots indicate better kinetics for ethanol electrooxidation in the presence of montmorillonite natural clays. The effect of some experimental factors such as the amount of MMT and Pt nanoparticles and the ethanol concentration were studied and the optimum conditions were obtained for electrooxidation of ethanol molecules using the FTO/MMT/Pt electrode.

In spite of the huge developments in analytical instrumentation during the past two decades, sample preparation is still considered as the most critical step in the whole analytical process. It is required in order to remove interferences and preconcentrate target analytes. Efforts have been made to improve selectivity during extraction. Molecularly-imprinted polymers (MIPs) have affinity for the original template molecule and have been used in applications, such as chemical separation, selective extraction, catalysis, or molecular sensing. In the present review, we describe the application of MIPs in the various modes of solid-phase microextraction.

A novel nano-adsorbent, magnetic carbon nanofibers (CNFs–Fe3O4), was prepared by impregnating magnetic Fe3O4 nanoparticles onto the surfaces of carbon nanofibers based on electrostatic interactions. The resulting nanoparticles were used as an adsorbent for the magnetic solid phase extraction of polycyclic aromatic hydrocarbons from environmental water samples. The experimental parameters affecting the extraction efficiency, including the amount of sorbent, desorption conditions, extraction time and salt concentration, were investigated and optimized. Under the optimal conditions, the detection limits of the method (S/N = 3) were in the range of 0.008–0.03 ng mL−1 and the limits of quantification (S/N = 10) were between 0.025 and 0.08 ng mL−1. The repeatability of the method was assessed through five consecutive extractions of independently prepared compound solutions at concentrations of 0.1, 10, and 100 ng mL−1. The observed repeatability ranged between 3.2% and 11.2%, depending on the considered compounds. The developed method was successfully applied to real water samples while the relative recovery percentages obtained from the spiked water samples at three level concentrations (0.1, 10 and 100 ng mL−1) were from 90.1% to 100.9%.

This study proposes a simple method for the preparation of a graphene oxide (GO) nano-sheet modified solid-phase microextraction (SPME) fiber via a sol–gel technique. For the first time, the prepared polyethylene glycol–graphene oxide (PEG–GO) sol–gel coating was applied for the analysis of aromatic amines in aqueous samples as target compounds. Important parameters that influence the extraction efficiency, such as desorption temperature and time, extraction temperature, extraction time, stirring speed, salting effect and pH, were investigated and optimized in detail. Under optimized condition, the linearity for the analytes was in the concentration range of 0.001 to 200 ng mL−1. Limits of detection (S/N = 3) of between 0.0003 to 0.2 ng mL−1 were obtained. The relative standard deviation (RSD) values for one fiber (repeatability) (n = 5) ranged from 4.2 to 6.6% and reproducibility between fibers (n = 3) was found to be below 8%. The developed method was successfully applied to real water samples, while relative recoveries obtained for spiked water samples ranged from 92.6 to 107.4%.

For the first time, a polypyrrole-carbon nanotubes-silicon dioxide composite film coated on a steel wire was prepared by an electrochemical method. Scanning electron microscopy images showed that this composite film was even and porous. The prepared fiber was used as an absorbent for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and o-xylene, followed by gas chromatographic analysis. This method presented an excellent performance, which was much better than that of a polypyrrole-carbon nanotube fiber. It was found that under the optimized conditions, the linear ranges were 0.01-200 ng/mL with correlation coefficients >0.9953, the detection limits were 0.005-0.020 ng/mL, the relative standard deviations were 3.9-6.4% for five successive measurements with a single fiber, and the reproducibility was 5.5-8.5% (n = 3). Finally, the developed method was successfully applied to real water samples, and the relative recoveries obtained for the spiked water samples were from 91.0 to 106.7%.

We have prepared a new material for solid-phase microextraction (SPME) of volatile aromatic hydrocarbons by electropolymerization of pyrrole, carbon nanotubes, and titanium oxide on the surface of a stainless steel wire. This fiber-like wire was used for the headspace solid-phase microextraction of mixtures of benzene, toluene, ethylbenzene, and o-xylene (BTEX), followed by their quantitation by GC with FID detection. The fiber is easily prepared, robust, thermally stable, and has good extraction efficiency. Under optimal conditions, the detection limits (at an SNR of 3) are in the range from 0.01 to 0.04 ng mL−1, and the limits of quantification (at an SNR of 10) are between 0.03 and 0.09 ng mL−1. The relative standard deviations (RSDs) for one fiber (i. e. the repeatability; for n = 5) range from 3.5 to 5.6 %, while the RSDs between fibers or from batch to batch (i.e. the reproducibility; for n = 3) are in the range from 5.9 to 8.1 %. The method was successfully applied to (spiked) real water samples, the relative recovery percentages being between 93.7 and 106.2 %.

A headspace solid-phase microextraction method was developed for the preconcentration and extraction of methyl tert-butyl ether. An ionic-liquid-mediated multiwalled carbon nanotube–poly(dimethylsiloxane) hybrid coating, which was prepared by covalent functionalization of multiwalled carbon nanotubes with hydroxyl-terminated poly(dimethylsiloxane) using the sol–gel technique, was used as solid-phase microextraction adsorbent. This innovative fiber exhibited a highly porous surface structure, high thermal stability (at least 320°C) and long lifespan (over 210 uses). Potential factors affecting the extraction efficiency were optimized. Under the optimum conditions, the method LOD (S/N = 3) was 0.007 ng/mL and the LOQ (S/N = 10) was 0.03 ng/mL. The calibration curve was linear in the range of 0.03–200 ng/mL. The RSDs for one fiber (repeatability, n = 5) at three different concentrations (0.05, 1, and 150 ng/mL) were 5.1, 4.2, and 4.6% and for the fibers obtained from different batches (reproducibility, n = 3) were 6.5, 5.9, and 6.3%, respectively. The developed method was successfully applied to the determination of methyl tert-butyl ether in different real water samples on three consecutive days. The relative recoveries for the spiked samples with 0.05, 1, and 150 ng/mL were between 94–104%.

An efficient and inexpensive semi-micro liquid–liquid extraction method has been developed for simultaneous clean-up and extraction of vitamin A and vitamin E in infant milk formula samples. After saponification of milk samples, extraction procedure was done in a 5-mL volumetric flask. 4.5 mL of saponified sample solution was added to the volumetric flask, and then 300 µL of organic solvent was added slowly to the surface of the saponified solution in the neck of the flask by a gas tight micro syringe. The mixture was agitated during the extraction time. After the extraction time a prescribed amount of organic phase was withdrawn, evaporated and reconstituted with methanol and finally was injected into the HPLC system for analysis. The proposed method provided good reproducibility (3.9–5.1%), good linearity (0.006–80 µg mL−1 for vitamin A and 0.1–400 µg mL−1for vitamin E), low detection limits (0.003 µg mL−1 for vitamin A and 0.08 µg mL−1 for vitamin E), and was a simple, low cost, efficient, and easy han...

The aim of this research was to develop a low price and environmentally friendly adsorbent with abundant of source to remove methylene blue (MB) from water samples. Sawdust solid-phase extraction coupled with high-performance liquid chromatography was used for the extraction and determination of MB. In this study, an experimental data-based artificial neural network model is constructed to describe the performance of sawdust solid-phase extraction method for various operating conditions. The pH, time, amount of sawdust, and temperature were the input variables, while the percentage of extraction of MB was the output. The optimum operating condition was then determined by genetic algorithm method. The optimized conditions were obtained as follows: 11.5, 22.0 min, 0.3 g, and 26.0°C for pH of the solution, extraction time, amount of adsorbent, and temperature, respectively. Under these optimum conditions, the detection limit and relative standard deviation were 0.067 μg L−1 and

A novel ‘ionic liquid-mediated multi-walled carbon nanotube (MWCNT)-poly(dimethylsiloxane) (PDMS)’ hybrid coating was prepared by the covalent functionalization of MWCNTs with hydroxyl-terminated PDMS using the sol–gel technique. The prepared fiber was successfully used for the separation and determination of trace amounts of polycyclic aromatic hydrocarbon compounds (PAHs) in four urine samples using head-space solid-phase microextraction coupled to gas chromatography-flame ionization detection. The proposed fiber has high thermal stability and long durability and it can be used more than 210 times without any significant change in its sorption properties. The effects of important parameters such as the exposure time, sampling temperature, sample ionic strength and stirring rate on the extraction efficiency have been studied and optimized. Under the optimal conditions, the method detection limits (S/N = 3) were in the range of 0.0005–0.004 ng mL−1 and the limits of quantification (S/N = 10) between 0.002 and 0.01 ng mL−1. The relative standard deviations for one fiber (repeatability, n = 5) were 4.9–7.5 % and for the fibers obtained from different batches (reproducibility, n = 3), 6.1–8.9 %. The developed method was successfully applied to determine trace levels of PAHs in real urine samples. The obtained relative recoveries for the spiked samples with 0.05 ng mL−1 of each of the PAH compounds were 89.3–107.2 %.

Ionic liquid mediated sol–gel sorbents for head-space solid phase microextraction (HS-SPME) were developed for the extraction of benzene, toluene, ethylbenzene and o-xylene (BTEX) compounds from water samples in ultra-trace levels. The analytes were subsequently analyzed with gas chromatography coupled to flame ionization detector (GC-FID). Three different coating fibers were prepared including: poly(dimethylsiloxane) (PDMS), coating prepared from poly(dimethylsiloxane) in the presence of ionic liquid as co-solvent and conditioned at a higher temperature than decomposition temperature of ionic liquid (PDMS-IL-HT) and coating prepared from poly(dimethylsiloxane) in the presence of ionic liquid as co-solvent and conditioned at a lower temperature than decomposition temperature of ionic liquid (PDMS-IL-LT). Prepared fibers demonstrate many advantages such as high thermal and chemical stabilities due to the chemical bonding of the coatings with the silanol groups on the fused-silica surface fiber. These fibers have shown long life time up to 180 extractions. The scanning electron micrographs of the fibers surfaces revealed that addition of ionic liquid into the sol solution during the sol–gel process increases the fiber coating thickness, affects the form of fiber structure and also leaves high pores in the fiber surface that cause high surface area and therefore increases sample capacity of the fibers. The important parameters that affect the extraction efficiency are desorption temperature and time, sample volume, extraction temperature, extraction time, stirring speed and salt effect. Therefore these factors were investigated and optimized. Under optimal conditions, the dynamic linear range with PDMS-IL-HT, PDMS and PDMS-IL-LT fibers were 0.3–200,000; 50–200,000 and 170–150,000 pg mL−1 and the detection limits (S/N = 3) were 0.1–2 and 15–200 and 50–500 pg mL−1, and limit of quantifications (S/N = 10) were 0.3–8 and 50–700 and 170–1800, respectively. The relative standard deviations (RSD) for one fiber (repeatability) (n = 5), were obtained from 3.1 up to 5.4% and between fibers or batch to batch (reproducibility) (n = 3) in the range of 3.8–8.5% for three fibers. The developed method was successfully applied to the real water samples while the relative recovery percentages obtained for the spiked water samples at 20 pg mL−1 were from 91.2 to 103.3%.

Mercury exists in two forms in environment, inorganic salts and organic compounds. Determination of mercury is very important, due to its health effects. In the present research, diphenylation of mercury using phenylboronic acid as a derivatization reagent was used for the determination of Hg(II) in real water samples. A simple, rapid and cheap method named dispersive liquid–liquid microextraction was used for the extraction of analyte under the following conditions: extraction solvent 16 μL of carbon tetrachloride, disperser solvent 1 mL of ethanol and sample volume 5 mL. Under the optimal conditions, the enrichment factor for diphenylmercury was 931 and the limit of detection calculated on the basis of five replicates was 0.004 μg mL−1. The repeatability of the method expresses as relative standard deviation was 5.1 (n = 6). The linear range was between 0.01 and 10 μg mL−1. The performance of the proposed technique was evaluated for the determination of mercury in different environmental water samples.

In this research, the headspace solid-phase microextraction (SPME) coupled with GC flame ionization detector was applied for the determination of some monocyclic aromatic amines in real water and urine samples. A sol-gel technique was applied for the preparation of the SPME fibers. Two different sol-gel coatings, (PEG and poly(ethylene glycol) modified with multi-walled carbon nanotubes [PEG/CNTs]), were prepared and compared. Extraction efficiency of PEG/CNTs was better than PEG fiber in the same conditions. To obtain maximum extraction efficiency, some parameters such as desorption temperature and time, temperature and time of extraction, salt effect, pH, and stirring speed were investigated and optimized for PEG/CNTs fiber. Under optimized conditions, the LODs (S/N = 3) were in the range of 0.5-50 ng/L and limits of quantification (S/N = 10) were between 1 and 500 ng/L. Repeatability (n = 5) was in the range of 3.2-9.1% and reproducibility (n = 3) was obtained from 5.5 to 12.0%. The method was successfully applied to the analysis of real water and urine samples with recoveries from 63.7 to 97.0%.

A method termed pseudo-stir bar hollow fiber solid/liquid phase microextraction (HF-SLPME) was utilized to extract three β-blockers—atenolol, metoprolol, and propranolol—in environmental waters. The extracted β-blockers were then separated, identified, and quantified by high-performance liquid chromatography with fluorescence detection. In HF-SLPME a porous polypropylene hollow fiber filled with MWCNTs reinforced organic solvent that acts as an analyte trap to pre-concentrate β-blockers from water samples. Both ends of the hollow fiber segment are sealed with magnetic stoppers. This device is placed inside the aqueous feed solution and plays the rule of a pseudo-stir bar. The effective parameters are optimized. The extracted β-blockers were analyzed at room temperature by high-performance liquid chromatography-fluorescence detection. The results showed that practical pre-concentration factors varied from 25.2–822. Under the optimized extraction conditions, the method showed good linearity and low limits o...

An in situ derivatization and solid-phase microextraction (SPME) method based on sol-gel technology coupled with gas chromatography– flame ionization detection was proposed for the determination of mercury [Hg(II)] at ultra-trace levels in water samples. The analytical procedure involves aqueous-phase derivatization of Hg(II) with phenylboronic acid in a sample vial and subsequent extraction with a sol-gel fiber coating. In this study, poly(ethylene glycol), modified with a coating fiber of multi-walled carbon nanotubes was used for the determination of mercury. The pH of the feed solution was kept at 5 with acetic acid–sodium acetate buffer solution. The optimized conditions are as follows: derivatization time, 10 min; extraction time, 60 min; extraction temperature, 408C; stirring rate, 1,000 rpm; sample volume, 5 mL. Under the optimal conditions, a detection limit of the method [signal-to-noise ratio (S/N) 5 3] were obtained at 0.001 ng/mL and a limit of quantification (S/N 5 10) were obtained at 0.005 ng/mL. Also, the relative standard deviations were obtained for one fiber (repeatability) (n 5 5) and between fibers or batch to batch (n 5 3) (reproducibility). The developed method was successfully applied to real water samples.

A simple, low-cost and sensitive method is demonstrated for derivatization and extraction of iodine from milk samples using hollow fiber liquid-phase microextraction (HF-LPME) and gas chromatography-electron capture detection. Iodide ions are converted to iodine under acidic medium and in the presence of an oxidant. The generated iodine reacted with 3-pentanone in extraction vial to give 2-iodo-3-pentanone and was extracted into 4 μL of 1-octanol located in the lumen of a hollow fiber. Organic solvent was selected using one variable at a time optimization method and the other main factors affecting derivatization and HF-LPME procedures were evaluated using a Taguchi’s L16 (45) orthogonal array. Under optimal conditions, the method showed low limit of detection (0.5 ng mL−1), wide linear range (1–2,000 ng mL−1) with good correlation coefficient (0.9997) and acceptable relative standard deviation (4.6 %, n = 5). Finally, the developed method was successfully applied for determination of iodide in real samples including infant milk formulas and cow milk with reasonable relative recoveries (99.8–110.5 %).

A new rapid, simple and effective cleanup procedure is demonstrated for the determination of ibuprofen, naproxen and diclofenac in urine samples by using hollow-fiber liquid membrane-protected solid-phase microextraction (HFLM-SPME) based on sol-gel technique and gas chromatography-flame ionization detector (GC-FID). In this technique, a sol-gel coated fiber was protected with a length of porous polypropylene hollow fiber membrane which was filled with water-immiscible organic phase. Subsequently the whole device was immersed into urine sample for extraction. Poly(ethylene glycol) (PEG) grafted onto multi-walled carbon nanotubes (PEG-g-MWCNTs) was used as extraction phase to prepare the sol-gel SPME fiber. Important parameters influencing the extraction efficiency such as desorption temperature and time, organic solvent, extraction temperature and time, pH, stirring speed and salt effect were investigated and optimized. Under the optimal conditions, the method detection limits (S/N=3) were in the range of 0.03-0.07ngmL(-1) and the limits of quantification (S/N=10) between 0.08 and 0.15ngmL(-1). Relative standard deviations for intra-day and inter-day precisions were 4.8-9.0% and 4.9-8.1%, respectively. Subsequently, the method was successfully applied to human urine fractions after administration of ibuprofen, naproxen and diclofenac.

Chitosan-grafted polyaniline was synthesized and applied as a sorbent for the preconcentration of phthalate esters in dispersive solid-phase extraction. By coupling dispersive solid-phase extraction with high-performance liquid chromatography and response surface methodology (central composite design), a reliable, sensitive, and cost-effective method for simultaneous determination of phthalate esters including dimethyl phthalate, di-n-butyl phthalate, and di(2-ethylhexyl)phthalate was developed. The morphology of sorbent had been studied by scanning electron microscopy and its chemical structure confirmed by Fourier transform infrared spectroscopy. Under optimum condition, good linearity was observed in the range of 5.0-5000.0 ng/mL. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were 0.1-0.3 and 0.3-1 ng/mL, respectively. The relative standard deviations were less than 8.8%. Finally, this procedure was employed for extraction of trace amounts of phthalic acid esters in milk samples, the relative recoveries ranged from 82 to 103%.

A simple, rapid, highly efficient, and reliable sample preparation method has been developed for the extraction and analysis of triazole pesticides from cucumber, lettuce, bell pepper, cabbage, and tomato samples. This new sorbent in the hollow-fiber solid-phase microextraction method is based on the synthesis of polyethylene glycol-polyethylene glycol grafted flower-like cupric oxide nanoparticles using sol-gel technology. Afterward, the analytes were analyzed by high-performance liquid chromatography with ultraviolet detection. The main parameters that affect microextraction efficiency were evaluated and optimized. This method has afforded good linearity ranges (0.5-50 000 ng/mL for hexaconazol, 0.012-50 000 ng/mL for penconazol, and 0.02-50 000 ng/mL for diniconazol), adequate precision (2.9-6.17%, n = 3), batch-to-batch reproducibility (4.33-8.12%), and low instrumental LODs between 0.003 and 0.097 ng/mL (n = 8). Recoveries and enrichment factors were 85.46-97.47 and 751-1312%, respectively.

A magnetic solid-phase extraction method coupled with gas chromatography was proposed for the determination of polycyclic aromatic hydrocarbons in the environmental water samples. The magnetic adsorbent was prepared by incorporating Fe3 O4 nanoparticles, multi-walled carbon nanotubes, and polypyrrole. The main factors affecting the extraction efficiency including the amount of the sorbents, desorption conditions, extraction time, salt concentration, and sample solution pH were investigated and optimized. Under the optimum conditions, good linearity was obtained within the range of 0.03-100 ng/mL for all analytes, with correlation coefficients ranging from 0.9942 to 0.9973. The method detection limits (S/N = 3) were in the range of 0.01-0.04 ng/mL and the limits of quantification (S/N = 10) were 0.03-0.1 ng/mL. Repeatability of the method was assessed through five consecutive extractions of independently prepared solutions at concentrations of 0.1, 10, and 100 ng/mL of the compounds. The observed repeatability ranged 3.4-10.9% depending of the compound considered. The proposed method was successfully applied in the analysis of PAHs in environmental samples (tap, well, river, and wastewater). The recoveries of the method ranged between 93.4 and 99.0%. The procedure proved to be efficient and environmentally friendly.

In the present work the combination of two liquid-phase microextraction techniques involving dispersive liquid-liquid microextraction and single-drop microextraction as a new pre-concentration technique is developed for the separation and determination of acidic non-steroidal anti-inflammatory pharmaceutical compounds, namely, naproxen, diclofenac, and ibuprofen, in water samples using high-performance liquid chromatography ultra violet-detection. The extraction conditions were optimized and, under the optimal conditions, the method showed good linearity range of 0.1-1000 μg L(-1) (R0.9990), acceptable reproducibilities (relative standard deviation% = 4.5-8.8%), low limits of detection (0.03-0.2 μg L(-1) ), and satisfactory relative recoveries. The developed method was applied for the determination of anti-inflammatory drugs in river and waste water samples.

In this study, a simple preparation approach was developed for modified bisphenol A (BPA) molecularly imprinted polymer sorbent used in the hollow fiber solid phase microextraction (MIP-HF-SPME) of chlorogenic acid (CGA). The pre-polymer solution containing the template was introduced into the polypropylene hollow fiber segment for in situ polymerization. MIP-HF-SPME conditions based on the modified MIP-sorbent were optimized. Finally, the tool was used for selective extraction of chlorogenic acid in Echinacea purpurea, a medicinal plant. Main parameters affecting synthesis of organic–inorganic hybrid MIP and microextraction procedure were investigated and optimized. The measurements were done under the optimal conditions. The limit of detection has been gained 0.08 ng/mL. The linear range and relative standard deviation (RSD %) are 0.2–1000 ng/mL and 0.38 ( n = 3) respectively. The average relative recoveries of spiked analyte in the four concentration levels were between 84.8 and 97.2%.

The headspace solid-phase microextraction (HS-SPME) method with two different coatings synthesized by sol–gel technology [such as poly(ethylene glycol) (PEG) and PEG reinforced with multi-walled carbon nanotubes (PEG/CNTs)] coupled with gas chromatography–flame ionization detector (GC–FID) was proposed for the determination of furan at trace levels in food samples. Under optimized conditions, the linear range for furan with PEG and PEG/CNTs fibers was 0.005–10 and 0.0005–10 ng/mL, the limit of detection ( S / N = 3) was 0.001 and 0.00025 ng/mL and the limit of quantification (LOQ) was 0.005 and 0.0005 ng/mL, respectively. For PEG and PEG/CNTs fibers, repeatability ( n = 5) was 6.2% and 4.9% and reproducibility ( n = 3) was 6.6% and 5.3%, respectively. Relative recoveries for the spiked samples with 0.1 ng/mL of furan were ranged from 92% to 103%. The proposed HS-SPME–GC–FID method was successfully applied for the extraction of furan in two environmental food samples (baby food and fruit juice).

In this study, poly(ethylene glycol) (PEG) grafted multi-walled carbon nanotubes (PEG-g-MWCNTs) were synthesized by the covalent functionalization of MWCNTs with hydroxyl-terminated PEG chains. PEG-g-MWCNTs was used as a novel stationary phase to prepare the sol–gel solid-phase microextraction (SPME) fiber in combination with gas chromatography–flame ionization detector (GC–FID) for the determination of ibuprofen, naproxen and diclofenac in real water samples. Some parameters which influencing the extraction efficiency were such as desorption temperature and time, extraction temperature and time, pH, salt effect and stirring speed that were investigated and optimized. Under the optimal conditions, the method detection limits (S/N = 3) were in the range of 0.007–0.03 ng mL−1 and the limits of quantification (S/N = 10) between 0.05 and 0.07 ng mL−1. The relative standard deviations (RSDs) for one fiber (repeatability) (n = 5) were obtained from 5.9 up to 8.1% and between fibers or batch to batch (n = 3) (reproducibility) in the range of 7.2–9.1%. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples at 0.2 ng mL−1 were from 84 to 107%.

A two phase hollow fiber liquid phase microextraction (HF-LPME) and gas chromatography mass spectrometry (GC-MS) method for the separation and determination of triazole fungicides, namely, penconazole, hexaconazole, diclobutrazole and diniconazole, is described. The extraction conditions were optimized for the four triazole fungicides as follows: extractant solvent, toluene; extraction time, 20 min; stirring rate, 720 rpm; no salt addition; and no pH adjustment. Under the optimal extraction conditions, the method showed good linearity (r2 = 0.997–0.999), acceptable reproducibility (RSD% = 6–9%), low limit of detection (0.3–0.8 μg·L–1), and satisfactory relative recoveries. The linear range is 1–5000 μg·L–1. The developed HF-LPME method was applied for the determination of triazole fungicides in farm, river, and tap water and also grape juice samples.

This review covers recent developments in surfactant-based extraction methods, with the aim of highlighting some of the most important aspects of micellar systems together with their applications in analysis. It also compares the phase-transfer methodology of different surfactant-based extraction methods (e.g., cloud-point extraction) with coacervative extraction methods using different kinds of surfactant. It includes factors affecting the extraction efficiency of the methods in some recent applications.

The combination of liquid phase microextraction (LPME) based on a single drop and gas chromatography flame ionization detector (GC-FID) was used for separation and determination of amitriptyline and nortriptyline in human plasma and urine samples. The sample solution was kept alkaline (pH 12), then a microdrop of organic solvent (isooctane) was suspended in the donor solution; after extraction, the organic microdrop was injected into the GC-FID. Experimental LPME conditions were optimized. Finally, the enrichment factors (89.5–139.0), the relative standard deviation (RSD%, n = 5) 1.1–8.5, linearity ranges (0.05–20 μg mL−1), and the limits of detections (0.01, 0.02 μg mL−1) for selected drugs were evaluated.

A new sample preparation method named directly suspended droplet liquid-liquid-liquid phase microextraction was used in this research for determination of three chlorophenols in environmental water samples. The analytes (2-chlorophenol, 3-chlorophenol and 4-chlorophenol) were extracted from 4.5 mL acidic donor phase, (pH 2, P1) into an organic phase, 350 µL of benzene/1-octanol (90 : 10 v/v, P2) and then were back-extracted into a 7 µL droplet of an basic (pH 13) aqueous solution (acceptor phase, P3). In this method, contrary to the ordinary single drop liquid-phase microextraction technique, an aqueous large droplet is freely suspended on the surface of the organic solvent, without using a microsyringe as supporting device. This aqueous microdroplet is delivered at the top-centre position of an immiscible organic solvent which is laid over the aqueous donor sample solution while the solution is being agitated. Then, the acceptor phase containing chlorophenols was withdrawn back into a HPLC microsyringe a...