Desorption Volume Research Articles

Fabrication of superparamagnetic adsorbent based on layered double hydroxide as effective nanoadsorbent for removal of Sb (III) from water samples.

In this study, the superparamagnetic adsorbent as Fe@Mg‐Al LDH was synthesised by different methods with two steps for the removal of heavy metal ions from water samples. An easy, practical, economical, and replicable method was introduced to remove water contaminants, including heavy ions from aquatic environments. Moreover, the structure of superparamagnetic adsorbent was investigated by various methods including Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and vibrating sample magnetometer. For better separation, ethylenediaminetetraacetic acid ligand was used, forming a complex with antimony ions to create suitable conditions for the removal of these ions. Cadmium and antimony ions were studied by floatation in aqueous environments with this superparamagnetic adsorbent owing to effective factors such as pH, amount of superparamagnetic adsorbent, contact time, sample temperature, volume, and ligand concentration. The model of Freundlich, Langmuir, and Temkin isotherms was studied to qualitatively evaluate the adsorption of antimony ions by the superparamagnetic adsorbent. The value of loaded antimony metal ions with Fe@Mg‐Al LDH was resulted at 160.15 mg/g. The standard deviation value in this procedure was found at 7.92%. The desorption volume of antimony metal ions by the adsorbent was found to be 25 ml. The thermodynamic parameters as well as the effect of interfering ions were investigated by graphite furnace atomic absorption spectrometry.

Development of a needle trap device packed with the Schiff base network-1/single-walled carbon nanotube for sampling phenolic compounds in air

This paper introduced needle traps filled with the new Schiff base network-1/single-walled carbon nanotube (SNW-1/SWCNT) adsorbent for sampling and analyzing phenolic compounds (phenol, 3-chlorophenol, o-cresol, and p-cresol) in air. In this perusal, the SNW-1/SWCNT adsorbent was synthesized and packaged using a 22-gauge spinal needle. This approach was first examined inside the laboratory and then applied in the field for real sampling. A 3-inlet container was placed on a heater at a specific temperature to produce different concentrations of phenolic compounds. The response surface methodology and central composite design methods were used to evaluate the desorption and breakthrough volume parameters of needle trap device packed with SNW-1/SWCNT. The Limit of detection and limit of quantitation values of this technique were 0.002–0.011 ng/ml and 0.008–0.037 ng/ml, respectively, indicating that the proposed sampler had very high sensitivity. The maximum response of the peak area was obtained at the extraction temperature of 270 °C and the extractions time of 5 min. The current technique was compared to the NIOSH-2546 method, and an R2 of 0.9812 was obtained between the two methods. The proposed method was used to determine the concentration of target compounds in the air of a plastic factory. The results showed that the concentration was less than the threshold limit values for phenolic compounds. SNW-1/SWCNTs have selectivity and the proposed method is a one-step procedure for analyzing phenolic compounds from the air.

Vortex-Assisted Dispersive Molecularly Imprinted Polymer-Based Solid Phase Extraction of Acetaminophen from Water Samples Prior to HPLC-DAD Determination

In the present study, acetaminophen (ACT) molecularly imprinted polymer (ACT-MIP) were successfully synthesized via surface imprinting polymerization. The structural and morphological properties of ACT-MIP were characterized using various analytical techniques. ACT-MIP were used as an adsorbent in a vortex-assisted dispersive molecularly imprinted solid-phase micro-extraction (VA-d-μ-MISPE), coupled with a high-performance liquid chromatography–diode array detector (HPLC-DAD) method for the determination of ACT in water samples. Influential parameters such as the mass of adsorbent, vortex speed, extraction time, desorption volume, and desorption time were optimized using a multivariate approach. Under optimum conditions, the maximum binding capacities of ACT-MIP and NIP (non-imprinted polymers) were 191 mg/g and 71.5 mg/g, respectively. The linearity was attained across concentrations ranging from 0.630 to 500 µg/L, with a coefficient of determination of 0.9959. For ACT-MIP, the limit of detection (LOD) and limit of quantification (LOQ), enhancement factor, and precision of the method were 0.19 ng/L, 0.63 ng/L, 79, and <5%, respectively. The method was applied in the analysis of spiked water samples, and satisfactory percentage recoveries in the range of 95.3–99.8% were obtained.

A new configuration for in-tube solid phase microextraction based on a thin-film coating

In the present research, in-tube solid phase microextraction and thin-film microextraction were combined in a new configuration in order to use the advantages of both techniques. For this purpose, poly(ortho-phenylenediamine) thin-film was electrodeposited on stainless-steel sheets. The sheets were inserted into a cartridge. The resulting configuration was used for in-tube solid phase microextraction of chlorophenols as model analytes. The analytes were separated and detected by high performance liquid chromatography coupled with ultraviolet detection. The important factors affecting the extraction such as the pH (6) and salt concentration of the sample solution (0%), extraction time (15 min), extraction and desorption flow rates (6 mL min−1 and 70 µL min−1, respectively), and desorption solvent type and volume (methanol, 500 µL) were optimized. The presented method can detect model analytes at concentrations as low as 0.3 µg L−1. The method showed good linearity in the range of 0.8–100.0 µg L−1 of chlorophenols with coefficients of determination better than 0.9945. The intraday and interday precisions were in the range of 1.3–5.8% and 3.5–8.3%, respectively. The tube-to-tube repeatability of the method was lower than 13.0%. Finally, the validated method was successfully used for the analysis of the selected analytes in real samples including rain water and honey.

A novel model to determine gas content in naturally fractured shale

A shale reservoir’s gas content is an indispensable, crucial parameter used in exploration, formation evaluation, block selection and exploitation. Canister gas desorption measurements are used to quantify lost gas volumes that are key to determine the gas content of the reservoir Usually, a lost gas volume is evaluated using the United States Bureau of Mines (USBM) direct method and/or a polynomial curve-fitting method. These methods extrapolate desorption data to time zero in the curve of a cumulative desorption volume versus the square root of time. Lost gas time is the time spent lifting the core out of a hole, handling and placing it inside a canister for evaluation., For cores with densely developed natural fractures, neither the USBM method nor the polynomial curve-fitting method can accurately estimate the lost gas volume if the lifting, handling and canister storage takes a long time. The lost gas period is a non-isothermal gas desorption process; the surrounding temperature keeps declining. Experiments were conducted to determine the methane desorption volumes of a Duvernay shale sample under various pressures and temperatures. Using Boyle’s law and the multilayer adsorption model, a novel mathematical model was built to calculate lost gas volume, including free gas and desorption gas. Because gas desorption is an endothermic procedure, equations for the inhaled energy were developed to overcome the van der Waals force between the molecules, deorbit the vibration equilibrium and the migration of molecules into the air. Finally, a shale sample with dense natural fractures from the Duvernay formation of Alberta, Canada, was used to validate the mathematical model. For comparison, the results from the USBM method, polynomial curve-fitting method and model’s calculations are illustrated in tables and figures. The outcomes exposed the results from the USBM method and polynomial curve-fitting method as deviating from the real gas content in the Duvernay formation without the consideration of the free gas loss. The model is reliable for performing gas content evaluations because it considers dual-pore structure, PVT behaviour and free gas escape simultaneously.

A microchip device based liquid-liquid-solid microextraction for the determination of permethrin and cypermethrin in water samples

In this work, for the first time, a microchip device integrating liquid-liquid-solid phase microextraction is presented. As a novel approach to microchip systems, liquid-liquid-solid microextraction was performed in a sandwiched microchip device. The microchip device consisted of three poly(methyl methacrylate) layers along with a double “Y”-shaped microchannel. As the stationary phase, polyacrylonitrile-C18 was synthesized and immobilized in the upper channel, while the beneath channel was used as a reservoir for the stagnant volume ratio of sample-to-extraction solvent phase. In this way, analytes were extracted from an aqueous sample through an organic phase into the stationary phase. The analytes were finally desorbed with a minimum amount of acetonitrile as the desorption solvent. Permethrin and cypermethrin were selected as the model analytes for extraction and subsequent analysis by gas chromatography-flame ionization detection. Under optimum conditions (extraction solvent; n-hexane, sample -to-extraction solvent volume ratio; 2:1, extraction time; 20 min, desorption solvent; acetonitrile, desorption volume; 200 μL, and desorption time; 15 min) detection limits were 3.5 and 6.0 ng mL−1 for permethrin and cypermethrin, respectively. Relative standard deviations for intra- and inter-day reproducibility were below 8.3%. Device-to-device precision was in the range of 8.1–9.6%. The proposed microchip device was successfully applied to determine permethrin and cypermethrin in water samples with recoveries in the range of 73–96%.

Experimental Research on the Effect of Ultrasonic Waves on the Adsorption, Desorption, and Seepage Characteristics of Shale Gas.

Shale gas reservoirs are tight reservoirs with ultralow porosity and ultralow permeability, and their matrix pores are mostly nanoscale. In addition, matrix particles and organic pore surfaces adsorb shale gas. These problems cause the production per well of shale gas to be lower than that of conventional natural gas. The use of hydraulic fracturing technology to exploit shale gas can achieve a good production increase effect. However, using this technology has some limitations caused by technical characteristics and geological conditions. Therefore, new technologies for shale gas exploitation need to be explored. In this study, we propose a method to improve the flow characteristics of shale gas by using ultrasonic waves to increase shale gas production and perform experimental tests to research the actual effect of this method. The lithology, mineral composition, pore structure, specific surface area, and pore size distribution of shale samples are tested. Then, the attenuation characteristics of ultrasonic waves propagating in shale are analyzed. Finally, the effect of ultrasonic waves on the adsorption, desorption, and seepage of shale gas is explored. Results show that the Langmuir adsorption isotherm can describe the adsorption characteristics of shale gas under the action of ultrasonic waves. The gas adsorption constant decreases with increasing ultrasonic wave power. The ultrasonic waves accelerate the gas desorption rate, significantly increase the desorption volume, and prolong the time taken to reach desorption equilibrium. They also increase the permeability of shale gas, and the growth is proportional to the power of the ultrasonic waves. These results indicate that the permeability of shale gas has a power function relationship with the effective stress under ultrasonic waves.

High-throughput biomonitoring of organophosphate flame-retardant metabolites in urine via 96-blade solid-phase microextraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry

Organophosphate flame retardants (OPFRs) are widely used in consumer products and building materials, but their propensity for migration poses a problem with respect to polluting indoor environments, water, soil, and dust. OPFR metabolites in urine samples are appropriate biomarkers for assessing exposure risk levels. In this paper, a high-throughput method that couples 96-blade solid-phase microextraction with ultra-performance liquid chromatography-tandem mass spectrometry (SPME-UPLC-MS/MS) is applied for the simultaneous detection of four OPFR metabolites in urine samples. The results indicated that the best extraction was achieved using 96 blades coated with hydrophilic-lipophilic balance weak anion exchange (HLB-WAX). The proposed SPME method's extraction efficiency was maximized by optimizing extraction time, pH value, desorption solution, desorption volume, and desorption time, and it was validated in accordance with the Food and Drug Administration's guidelines. The findings indicated that the proposed method has a wide linearity range (0.5–100 ng mL−1) and low detection limits (0.09–0.14 ng mL−1). The method's accuracy ranged from 98% to 118%, with intra-day precision ranging from 1% to 10%. In contrast, inter-day precision ranged from 3% to 16%. Accuracy was also evaluated using independent urine samples, which ranged from 78% to 124% with corresponding relative standard deviations (1%–16%). Ultimately, DoCP was detected in two real samples at a concentration of 0.5–1.1 ng mL−1, and BEHP was detected at a concentration of 0.2–1.2 ng mL−1. Overall, the proposed SPME-UPLC-MS/MS method is reliable, accurate, and capable of simultaneously determining four OPFR metabolites in urine samples and screening them to assess exposure risk for humans.

Application of polyethylene glycol-coated iron oxide nanoparticles for magnetic solid phase extraction of copper from seawater samples and its determination by graphite furnace atomic absorption spectrometry using response surface methodology for optimization of extraction

In this research, a novel solid phase extraction method combined with graphite furnace atomic absorption spectrometry has been employed for the extraction and trace determination of copper in tap and seawater samples. The technique was based on poly ethylene glycol-coated iron oxide nanoparticle as adsorbent for solid phase extraction of copper ions. Optimal conditions including pH, extraction and desorption time, concentration and volume of eluent, temperature, volume of sample, amount of PEG and sorbent were investigated and optimized using both the one-variable-at-a-time method and response surface methodology. Under the optimal experimental conditions, the calibration graph was linear in range of 0.5–125.0 µg/L with detection limit of 6 ng/L. Good enrichment factor of 121 folds for the analyte was obtained. The repeatability of the method was satisfactory (RSD ≤ 4.8%). Finally a few seawater samples of Chabahar Bay (Southeast Iran) were analyzed successfully with proposed procedure.

Core-shell magnetic zeolite imidazolate framework-8 as adsorbent for magnetic solid phase extraction of brucine and strychnine from human urine

Core-shell magnetic zeolite imidazolate framework-8 (Fe3O4@PAA@ZIF-8) was successfully synthesized and first employed as adsorbent of magnetic solid-phase extraction (MSPE) for the determination of brucine and strychnine in human urine sample coupled with high performance liquid chromatography. The as-prepared Fe3O4@PAA@ZIF-8 was characterized by transmission electron microscopy, Fourier-transform infrared spectrometry, X-ray diffraction, vibrating sample magnetometer and zeta potential analysis. Main parameters affecting the MSPE efficiency, including amount of adsorbent, sample solution pH, extraction time, ionic strength, desorption solvent, desorption time and desorption volume were further optimized. Under the optimized conditions, the proposed method provided good linearity (5.0–1000.0 μg L−1) with determination coefficients between 1.0000 and 0.9998, low limits of detection in the range of 1.1–1.2 μg L−1, and excellent reproducibility with relative standard deviations of less than 7.7%. The intra-day and inter-day precision were 1.5–3.2% and 2.1–7.2%, respectively. Satisfactory spiked recoveries were between97.2% and 115.4% with the relative standard deviations less than 6.3%. The results demonstrated that Fe3O4@PAA@ZIF-8 composite was a promising magnetic adsorbent for the preconcentration of brucine and strychnine in human urine sample.

Experimental insights into the adsorption-desorption of CH4/N2 and induced strain for medium-rank coals

To support the understanding of the effect of N2-enhanced coalbed methane (N2-ECBM) application on medium-rank coals, four coal samples from Shanxi Province were selected to test the porosity, mechanical properties and strain induced by binary gas adsorption-desorption. The results show that the desorption hysteresis is weakened with increasing N2 fraction and is strengthened with increasing CH4 fraction, indicating that increasing the N2 fraction can reduce the selectivity of coal to CH4. The critical desorption pressure of a mixed gas increases in a high N2 fraction environment, promoting the desorption of CH4 and enhancing its recovery. This research clarifies the anisotropic strain characteristics induced by the adsorption-desorption of CH4/N2 and provides reliable data for anisotropic permeability numerical simulations in the N2-ECBM process. Swelling and shrinkage volume strain are negative-exponentially related to the N2 fraction, and the volume shrinkage strain is close to the volume swelling strain given a N2 fraction of 50%. There exists a polynomial relationship between the volume swelling/shrinking strain and adsorption capacity, which has a potential predictive effect on the volume strain variation in coal during N2-ECBM. The analysis of the adsorption volume swelling strain rate and desorption volume shrinkage strain rate indicates that the N2 fraction and micropore volume are the main factors controlling volume deformation. The volume strain decreases with increasing elastic modulus, but nitrogen injection weakens the effect of the elastic modulus on the strain. In this study, the desorption percentage increased and the volume swelling strain decreased with increasing nitrogen fraction. Nitrogen injection and sealing have a positive effect on methane desorption and the optimal N2 fraction should be greater than 50%. This work provides a reference for improving coalbed methane production.

Freestanding Fully Porous Polyimide Membrane for Thin Film Microextraction

In this study, freestanding fully porous polyimide (FFPP) membranes were prepared in batches by the scraping technique and vapor-induced phase separation (VIPS) and used for thin film microextraction (FFPP-TFME). When water vapor was applied simultaneously during scraping, the resulting membrane surface was highly porous, in contrast to the dense and smooth surface obtained without vapor. The micro/nanocomposite pore structure was revealed by scanning electron microscopy and nitrogen adsorption–desorption. The diameters of the micropores, nanopores and fibrous polyimide (PI) nanofibers were 0.5–1.5 μm, ca. 30 nm and ca. 250 nm, respectively. The extraction performance of the FFPP-TFME method was evaluated with organochlorine pesticides (OCPs) as model analytes in water. The extracted OCPs were desorbed in acetone and then quantified by gas chromatography–mass spectrometry. The effects of extraction time, ionic strength, desorption solvent, desorption volume and desorption time were investigated. Under the optimized conditions, the limits of detection (LODs) for eight OCPs (4.4–83 ng L−1), linear ranges (0.05–50 μg L−1), correlation coefficients (0.997–0.999), intrabatch relative standard derivations (RSDs, 0.88–9.20%) and interbatch RSDs (6.35–13.5%) were obtained. The method was also successfully applied to the analysis of environmental water samples, and the relative recoveries of all real water samples were 73.6–116.4%. These results show that the FFPP-TFME method is a simple, efficient and environmentally friendly method for the pretreatment of trace organic pollutants in water samples.

Preparation and application of Fe3O4@ SiO2@ poly (o-phenylenediamine) nanoparticles as a novel magnetic sorbent for the solid-phase extraction of tellurium in water samples and its determination by ET-AAS

A novel magnetic polymer (Fe3O4@ SiO2@ PoPD) is synthesized for the magnetic solid-phase extraction (MSPE) of tellurium from water samples and its determination by electrothermal atomic absorption spectroscopy (ET-AAS). The morphology, composition and magnetic properties of the synthesized nanoparticles are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometery (VSM). The factors affecting separation and preconcentration of tellurium including the amount of sorbent, composition of sorbent material, extraction time and temperature, desorption time and temperature, pH and ionic strength of the sample solution, desorption solvent type, concentration and volume are studied. Under optimized experimental condition, the linear range and the detection limit of the method are 0.08–1.9 ng mL−1 (R2 = 0.9879) and 0.05 ng mL−1, respectively. The percent recovery of tellurium from real samples spiked at 0.5 ng mL−1 is more than 98%. The intraday and interday relative standard deviations for a batch of the sorbent at above concentration level are 4.3 and 5.6%, respectively. The sorbent-to-sorbent RSD% is 8.9%. Finally, the developed method is successfully applied to the analysis of tellurium in some real samples.

The impact of an Amberlite XAD-16-based chelating resin for the removal of aqueous Cd(II) and Pb(II)ions

The main objective of this study is to investigate the influence of the Amberlite XAD-16-based chelating resin, 1,8-(3,6-dithiaoctyl)-4-polyvinylbenzenesulphonate (dpvbs), for the removal of the highly lethal Pb(II) and Cd(II) from aqueous solutions. The extractor`s behavior is examined, as adsorbent as well as coordinating agent showing structural changes upon the interaction with the targeted metal ions. Elemental analyses, FTIR, electronic spectra, EDS and XPS were used to provide a close image of the composition, structural and morphological changes upon the interaction with Pb(II) and Cd(II). Thermal behavior of the sorption products, compared with the coordinating resin, were also, studied and the estimated thermodynamic parameters indicated an endothermic spontaneous sorption mechanism. The BET surface area, BJH desorption volume and the pore diameters increased upon chelation with Cd(II) and Pb(II), indicating the destruction of the cross-linking of the free resin. SEM and AFM studies confirmed the surface morphological change of dpvbs, after sorption processes. The sorption effectiveness was examined utilizing batch and column methods, showing high removal efficiency with an average sorption of 99.9%. dpvbs was tested for the removal of metal ions from tap watershowing a metal uptake of almost the same after 3 cycles, with an efficiency of 98–99%.

Polyvinylidene difluoride film with embedded poly(amidoamine) modified graphene oxide for extraction of chlorpyrifos and diazinon

An effective, sensitive, relatively fast, and cost-effective method was developed to determine two types of selected organophosphorus pesticides (OPPs) including diazinon and chlorpyrifos in apple, peach, and four different water samples (river, sea, well, and agriculture wastewater samples) through applying poly(amidoamine)@graphene oxide-reinforced polyvinylidene difluoride thin-film microextraction (PAMAM@GO-PVDF-TFME). The extracted analytes were desorbed via organic solvent and determined using high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The strong interactions between the sorbent and selected analytes (coordination bonds, intermolecular hydrogen bonding, π-π interactions, and hydrophobic effects) made this TFME capable of high extraction performance and capacity. Several factors involved in the PAMAM@GO-PVDF-TFME experiments such as desorption volume, desorption time, sample pH, extraction time, and stirring rate were screened via Plackett-Burman design and then optimized through Box-Behnken design with the purpose of reaching the highest extraction efficiency. The above method showed a good linear range (0.5-500 μg L-1 and 1-500 μg L-1) with the coefficient of determination better 0.9944, low limits of determination (0.12 and 0.20 μg L-1), good enrichment factors (99 and 98), acceptable extraction recoveries (99 and 98%), and good spiking recoveries (90-98%) under the optimized condition at three different spike levels for chlorpyrifos and diazinon, respectively. The results confirmed that the presented method would be promising for the determination of various types of these pesticides in environmental and beverage samples.

Influence of coalification on methane diffusion dynamics in middle-high rank coals

ABSTRACT Understanding the effect of coalification on the diffusion of methane in middle-high rank coals (MHRC) is fundamental for optimizing the coalbed methane (CBM) drainage strategies. Safe coal mining relies critically on this approach. Hence, CH4 adsorption/desorption experiments and a new methane diffusion model were used to study methane diffusion behavior in five different metamorphic degree coals from China. The results indicate that, as the vitrinite reflectance (Ro) increase, the Langmuir volume (VL) shows a downward trend at first, then increases. Coalification especially for the third coalification jump (Ro = 1.26%) shows a turning effect on diffusion dynamics of MHRC. The desorption volume and initial diffusion coefficient (D0) both show a slight decreasing, then rapid increasing trend. The D0 of five coals jumps at Ro = 1.26%. VL increases alongside that of the micropores volume. With the decrease of the Raman parameter ID1/IG, the VL, methane desorption volume within 7200 s and D0 all increase. Results show that coalification changes the microporous structure and the macromolecular structure of the coal, which finally affects the diffusion capacity of coal. Coalification has a positive effect for the gas extraction and the development of CBM for the semianthracites.

Magnetic Fe3O4@SiO2@β-cyclodextrin for solid phase extraction of methyl parathion and fenthion in lettuce samples.

In this study, magnetic Fe3O4@SiO2@β-cyclodextrin copolymerized microparticles were synthesized and applied for the extraction of methyl parathion and fenthion in lettuce samples followed by HPLC-UV detection. The magnetic β-cyclodextrin copolymerized microparticles were prepared by dispersion polymerization with acryloyl β-cyclodextrin as the functional monomer and ethylene glycol dimethyacrylate as the crosslinker. The composite magnetic microparticles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, magnetic measurement, and thermogravimetric analysis, and used as the adsorbent of magnetic solid-phase extraction (MSPE) for methyl parathion and fenthion. The extraction conditions including sample pH and ionic strength, desorption solvent type and volume, and adsorption and desorption times were optimized. Under the optimal extraction conditions, an MSPE-HPLC-UV method was developed for the detection of methyl parathion and fenthion in lettuce. Wide linear ranges of 1.0-200 μg kg-1 (R2 = 0.9998) for methyl parathion and 1.5-200 μg kg-1 (R2 = 0.9978) for fenthion were obtained and the limits of detection were 0.3 μg kg-1 for methyl parathion and 0.5 μg kg-1 for fenthion in lettuce, respectively. The proposed method was applied for the determination of methyl parathion and fenthion in lettuce with satisfactory recoveries between 89.2-101.2%, and relative standard deviations were less than 9.1%. Thus, the MSPE-HPLC-UV method has high accuracy and sensitivity for the analysis of methyl parathion and fenthion in lettuce samples.

Glutathione-stabilized Fe3 O4 nanoparticles as the sorbent for magnetic solid-phase extraction of diazepam and sertraline from urine samples through quantitation via high-performance liquid chromatography.

The synthesis and application of glutathione-coated magnetic nanocomposite were introduced with the purpose of developing a stable, cheap, operationally convenient, simple, fast, sensitive, and selective device for the microextraction of diazepam and sertraline for the first time. The prepared glutathione@Fe3 O4 nanocomposite was used as the sorbent in the form of magnetic solid-phase extraction. Afterward, the extracted analytes were desorbed by organic solvent and analyzed by high-performance liquid chromatography-ultraviolet detection. Several influential variables such as desorption time, desorption volume, sample pH, extraction time, and sorbent amount were screened through Plackett-Burman design and then optimized via Box-Behnken design. The obtained results showed that the above-mentioned method enjoys a good linear range (0.2-500 μg/L) with the coefficient of determination higher than 0.9927, low limits of determination (0.07-0.24 μg/L), acceptable limits of quantification (0.22-0.93 μg/L), good enrichment factors (128 and 153), and good spiking recoveries (95-105%) for diazepam and sertraline under the obtained optimized condition. Analyzing the real samples results in the confirmation of the presented method and it can be applied for the analysis of various organic compounds in biological samples.

MIL-101 (Cr) @ graphene oxide-reinforced hollow fiber solid-phase microextraction coupled with high-performance liquid chromatography to determine diazinon and chlorpyrifos in tomato, cucumber and agricultural water

An effective, sensitive, relatively-fast and cost-effective method was developed to determine two types of selected organophosphorus pesticides (OPPs) including diazinon and chlorpyrifos in tomato, cucumber and agricultural water samples through applying MIL-101@ graphene oxide-reinforced hollow fiber solid-phase microextraction (MIL-101@GO–HF–SPME). The extracted analytes were desorbed via organic solvent and analyzed through high-performance liquid chromatography-ultraviolet detection (HPLC-UV) after extraction. MIL-101@ GO sorbent which was previously prepared and characterized was first dispersed in methanol by ultrasonication and then immobilized into the pores of a hollow fiber (HF). Several factors involved in MIL-101@GO–HF–SPME experiment such as desorption volume, ionic strength, desorption time, sample pH, extraction time and stirring rate were screened via Plackett–Burman design and then optimized through Box–Behnken design with the purpose of reaching the highest extraction efficiency. The above method showed a good linear range (1–500 μg L−1) with coefficient of determination higher than 0.9948, low limits of determination (LODs, 0.21 and 0.27 μg L−1), acceptable limits of quantifications (LOQs, 0.72 and 0.91 μg L−1), good enrichment factors (EFs, 49 and 41), acceptable absolute recoveries (AR%, 49 and 41%) and good spiking recoveries (88–104%) under the optimized condition at three different spiked levels for chlorpyrifos and diazinon, respectively. It is worth mentioning that due to the clean-up function of HF, there is no time-consuming sample pretreatment procedure (e.g. filtration or centrifugation) prior to the microextraction. Therefore, the presented method took advantage of both excellent adsorption performance of MIL-101@GO and the clean-up function of HF. The results confirmed that the presented method would be promising for the analysis of various types of these pesticides in environmental and vegetable samples.

Trace Extraction of Metoprolol from Plasma, Urine and EBC Samples Using Modified Magnetic Nanoparticles Followed by Spectrofluorimetric Determination for Drug Monitoring Purposes

Background: Metoprolol is a selective β1-adrenergic receptor antagonist (β-blockers). It is widely used for the treatment of hypertension and other related diseases. Metoprolol can be used as a doping agent in sports, thus has been included in the list of forbidden drugs. In Iran, therapeutic drug monitoring (TDM) of β-blockers is an applied procedure in some cases. A therapeutic regimen could be easily managed by the determination of drug levels in biological fluids which is a relatively costly process and requires highly skilled technical staff. Using a simple and low-cost analytical procedure may help to use TDM in routine clinical practice. Methods: A real biological sample was prepared and its pH was adjusted to 3-4, then metoprolol was quickly extracted using magnetic iron oxide nanoparticles (MIONPs) modified by sodium dodecyl sulfate (SDS) and determined by applying spectrofluorimetry at 340 ± 3 nm after excitation at 283 ± 3 nm. Results: The extraction and determination conditions including, the amount of MIONPs and SDS, pH of the solution, standing time, desorption solvent type and volume were investigated and adjusted. Calibration curves were linear over the concentration range of 6–100 ng/mL for plasma and 5–100 ng/mL for water, urine and exhaled breath condensate samples, respectively. Intra and inter-day precision values for determination of metoprolol in different samples were less than 5.6 % and 6 %, respectively, and accuracy (as a relative error) was better than 5 %. Moreover, standard addition recovery tests were carried out, and the analytical recoveries ranged from 86 % to 113 %. The limits of detection (LOD) and limits of quantification (LOQ) of metoprolol were found to be in the range of 2.1-3.4 ng/mL and 6.3- 10.2 ng/mL, respectively. Conclusion: The developed method was successfully applied to biological samples taken from a volunteer who was given an oral tablet of 50 mg metoprolol.