Determination of trace amounts of nystatin in water and vaccine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by high-performance liquid chromatography–ultraviolet detection

In this work, magnetic solid-phase extraction based on sodium dodecyl sulfate-coated Fe₃O₄ nanoparticles has been successfully applied for extraction and preconcentration of trace amounts of nystatin from water and vaccine samples prior to high-performance liquid chromatography–ultraviolet detection. Various experimental parameters affecting extraction and recovery of the analyte, such as the amount of sodium dodecyl sulfate, pH of the sample solution, salt concentration, extraction time, sample volume and desorption conditions, were systematically studied and optimized. Under optimized conditions, nystatin was quantitatively extracted. Proper linear range with good coefficient of determination, (R ² > 0.99) and limit of detection and quantification (based on signal-to-noise ratios of 3 and 10) of 2.0 and 5.0 µg L^?1, over the investigated concentration range (5–700 µg L^?1), were obtained, respectively. The intra-day and inter-day relative standard deviations at 50 µg L^?1 level of NYS were 1.4 and 4.5% based on six replicate determinations. The accuracy of the method was evaluated by recovery measurements on spiked samples. Suitable recoveries of 96–102 and 26–44% were achieved (at spiked levels of 50, 300 and 500 µg L^?1) for water and vaccine samples, respectively.     

Preparation,characterization, and applications of a novel solid-phase microextraction fiber by sol-gel technology on the surface of stainless steel wire for determination of poly cyclic aromatic hydrocarbons in aquatic environmental samples

A novel solid-phase microextraction(SPME) fiber was prepared using sol–gel technology with ethoxylated nonylphenol as a fiber coating material. The fiber was employed to develop a headspace SPME–GC–MS method suitable for quantification of 13 polycyclic aromatic hydrocarbons (PAHs) in water samples. Surface characteristics of the fibers were inspected by energy dispersive X-ray (EDX) spectroscopy as well as by scanning electron microscopy (SEM). The SEM measurements showed the presence of highly porous nano-sized particles in the coating. Important parameters affecting the extraction efficiency such as extraction temperature and time, desorption conditions as well as ionic strength have been evaluated and optimized. In the next step, the validation of the new method have been performed, finding it to be specific in the trace analysis of PAHs, with the limit of detection (LOD) ranging from 0.01 to 0.5 μg L⁻¹ and the linear range from the respective LOD to 200 μg L⁻¹with RSD amounting to less than 8%. The thermal stability of the fibers was investigated as well and they were found to be durable at 280 °C for 345 min. Furthermore, the proposed method was successfully applied for quantification of PAHs in real water samples.     

A theory of finite tensile deformation of double-network hydrogels

A continuum damage model was developed to describe the finite tensile deformation of tough double-network (DN) hydrogels synthesized by polymerization of a water-soluble monomer inside a highly crosslinked rigid polyelectrolyte network. Damage evolution in DN hydrogels was characterized by performing loading-unloading tensile tests and oscillatory shear rheometry on DN hydrogels synthesized from 3-sulfopropyl acrylate potassium salt (SAPS) and acrylamide (AAm). The model can explain all the mechanical features of finite tensile deformation of DN hydrogels, including idealized Mullins effect and permanent set observed after unloading, qualitatively and quantitatively. The constitutive equation can describe the finite elasto-plastic tensile behavior of DN hydrogels without resorting to a yield function. It was showed that tensile mechanics of DN hydrogels in the model is controlled by two material parameters which are related to the elastic moduli of first and second networks. In effect, the ratio of these two parameters is a dimensionless number that controls the behavior of material. The model can capture the stable branch of material response during neck propagation where engineering stress becomes constant. Consistent with experimental data, by increasing the elastic modulus of the second network the finite tensile behavior of the DN hydrogel changes from necking to strain hardening.     

Development and application of a new solid-phase microextraction fiber by sol–gel technology on titanium wire

Novel solid-phase microextraction fibers were prepared based on sol–gel technique. Commonly used fused silica substrate was replaced by titanium wire which provided high strength and longer fiber life cycle. Titanium isopropoxide was employed as the precursor which provides a sol solution containing Ti–OH groups and shows more tendencies to the molecularly similar group on the substrate. Three different polymers, poly (dimethylsiloxane) (PDMS), poly(ethylenepropyleneglycol)-monobutyl ether (Ucon) and polyethylene glycol (PEG) were employed as coating polymer in preparing three different fibers. The applicability of these fibers was assessed for the headspace SPME (HS-SPME) of benzene, toluene, ethylbenzene and xylenes (BTEX) from water sample followed by gas chromatography–mass spectrometry (GC–MS). Effects of different parameters such as fiber coating type, extraction condition, desorption condition were investigated and optimized. Under the optimized conditions, LODs and LOQs of 0.75–10 μg L⁻¹ (S/N = 3) and 1–20 μg L⁻¹ (S/N = 10) were respectively obtained. The method showed linearity in the range of 10–25,000 μg L⁻¹ with correlation coefficient of >0.99. The relative standard deviation was less than 8%.     

A high-throughput approach for the determination of pesticide residues in cucumber samples using solid-phase microextraction on 96-well plate

A high-throughput solid-phase microextraction (SPME) on 96-well plate together with gas chromatography–mass spectrometry (GC–MS) was developed for the determination of some selected pesticides in cucumber samples. Pieces with the length of 1.0 cm of silicon tubing were precisely prepared and then coated on the end part of stainless steel wires. The prepared fibers were positioned in a home-made polytetrafluoroethylene (PTFE)-based constructed ninety-six holes block to have the possibility of simultaneous immersion of the SPME fibers into the center of individual wells. Pesticides such as diazinon, penconazol, tebuconazol, bitertanol, malathion, phosalone and chlorpyrifos-methyl were selected for their highly application in cucumber field. The performances of the SPME fibers, such as intra and inter-fibers reproducibility, were evaluated and the results showed a good similarity in extraction yields. A volume of 1 mL of the aquatic supernatant of the cucumber samples was transferred into the 96-well plate and the array of SPME fibers was applied for the extraction of the selected pesticides. The important parameters influencing the whole extraction process including, organic solvent percent, salt addition, dilution factor, stirring rate and extraction time were optimized. The inter- and intra-day RSD% were found to be less than 15.4%. Limits of detection (LOD) and limits of quantification (LOQ) were below 60 and 180 μg kg⁻¹, respectively. The coefficient of determination was satisfactory (r² > 0.99) for all the studied analytes. The developed method was successfully applied to the monitoring of several samples gathered from local markets.     

Green synthesis of cerium oxide nanoparticle using Origanum majorana L. leaf extract,its characterization and biological activities

Cerium oxide nanoparticle (CeO-NP) was synthesized using Origanum majorana L. leaf extract and characterized using particle size analyzer, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR). The antioxidant properties and cytotoxic effects of CeO-NP in human breast carcinoma cells (MDA-MB-231 cell line) and human umbilical vein endothelial cells (HUVEC) as normal cells were evaluated. To determine the probable molecular mechanism of action of CeO-NP on cellular redox and anti-inflammatory potential, the expressions of antioxidant-related genes catalase (CAT), superoxide dismutase (SOD) in HUVEC cell line were also analyzed. The results indicated that spherically shaped nanoparticles with a size of 10–70 nm bound to functional phenolic and flavonoids from O. majorana L. leaf extract. The green synthesized CeO-NP showed antioxidant activity by free radical scavenging activity against DPPH and ABTS free radicals. The antioxidant activity was significantly (p < 0.001) lower than that of Butylated hydroxyanisole (BHA) as a reference antioxidant. The obtained results elucidated that CeO-NP possessed cytotoxicity. The cytotoxic effects of CeO-NP were higher against MDA-MB-231 cancer cells compared to HUVEC normal cells. In addition, this NP was capable to enhance the expression of CAT and SOD as main antioxidant-related genes. Consequently, the higher cytotoxic effects of CeO-NP against breast cancer compared to normal cells indicated the potential use of this NP as anti-cancer agent. However, more research on its cytotoxicity against other cancer cells and mechanisms in which this NP exert its anti-cancer properties should be performed.     

In situ solid-phase microextraction and post on-fiber derivatization combined with gas chromatography–mass spectrometry for determination of phenol in occupational air

A method based on solid-phase microextraction (SPME) followed by on-fiber derivatization and gas chromatography–mass spectrometry detection (GC–MS) for determination of phenol in air was developed. Three different types of SPME fibers, polar and non-polar poly(dimethylsiloxane) (PDMS) and polyethylene glycol (PEG) were synthesized using sol–gel technology and their feasibility to the sampling of phenol were investigated. Different derivatization reagents for post on-fiber derivatization of phenol were studied. Important parameters influencing the extraction and derivatization process such as type of fiber coating, type and volume of derivatizing reagent, derivatization time and temperature, extraction time, and desorption conditions were investigated and optimized. The developed method is rapid, simple, easy and inexpensive and offers high sensitivity and reproducibility. Under the optimized conditions, the detection limit of the method was 5 ng L⁻¹ using selected ion monitoring (SIM) mode. The inter-day and intra-day precisions of the developed method under optimized conditions were below 10%, and the method shows linearity in the range of 20 ng L⁻¹ to 500 μg L⁻¹with the correlation coefficient of >0.99. The optimized method was applied to the sampling of phenol from some biologics production areas. The compared results obtained using current and standard methods were shown to be satisfactory.     

Immersed solvent microextraction of aryloxyphenoxypropionate herbicides from aquatic media

An immersed solvent microextraction (SME) method was successfully developed for the trace enrichment of aryloxyphenoxypropionate herbicides from aquatic media. A microdrop of toluene was used as the extraction solvent. Some important extraction parameters such as type of solvent, solvent dropsize, stirring rate, ionic strength and extraction time were investigated and optimized. The microdrop volume of 1.5?µL, a sampling time of 25?min, and use of toluene were major parameters for achieving high enrichment factors. The linearity was studied by preconcentration of 4?mL of the water samples spiked with a standard solution of aryloxyphenoxypropionates at the concentration range of 0.15 to 30?ng?mL^?1. The coefficient of determination was satisfactory (r ^2?>?0.99) for all the studied analyte and the relative standard deviations (RSD%) values under the optimized condition were found to be 1.7 to 14.2% at the concentrations of 1 and 10?ng?mL^?1. The enrichment factors were from 217 to 403 for the samples spiked at 1?ng?mL^?1. Detection limits were obtained to be in the range of 0.05 to 0.15?ng?mL^?1 using time-scheduled selected ion monitoring (SIM). The EI mass spectra of these herbicides revealed that fenoxaprop-P-ethyl and quizalofop-P-ethyl exhibited [M-COOC₂H₅]⁺ as the base peak while, clodinafop-propargyl, haloxyfop-etotyl and haloxyfop-P-methyl showed [M-C₂H₄COOC₃H₃]⁺, [M-CH₂COOC₄H₈O]⁺ and [M-COOCH₃]⁺ as the base peaks, respectively. The developed method was successfully applied to the extraction and determination of aryloxyphenoxypropionates in river water samples.     

Simplified kinetic calibration of solid-phase microextraction for in vivo pharmacokinetics

Solid-phase microextraction (SPME) has been demonstrated to be useful for in vivo sampling in pharmacokinetic studies. In this study, a single time-point kinetic calibration for in vivo dynamic monitoring was developed by simplification of the laborious multiple time-point kinetic calibration, based on the independent desorption kinetics of the preloaded standards from SPME fibers with the changing analyte concentrations. The theoretical foundation and practical application conditions, such as the replicate numbers, the optimal time-point for desorption, and the sampling time, were systematically investigated. Furthermore, the feasibility of using regular standards rather than deuterated ones for the kinetic calibration was justified by comparing to the data obtained using the deuterated standards. All the methods were verified by in vitro and in vivo experiments. The results from in vivo SPME were validated by the blood drawing and chemical assay. These simplified calibration methods improved the quantitative applications of SPME for dynamic monitoring and in vivo sampling, enhance the multiplexing capability and automatic potentials for high throughput analysis, and decrease expenses on reagents and instruments.     

Biological synthesis and characterization of gold nanoparticles using Verbascum speciosum Schrad. and cytotoxicity properties toward HepG2 cancer cell line

Research on Chemical Intermediates - Gold nanoparticles (AuNPs) are considered as one of the best modes of drug releasing plans for the treatment of various diseases. AuNPs have different...