Maryam Karimi

Application of response surface method for optimization of dispersive liquid-liquid microextraction of water-soluble components of Rosa damascena Mill. essential oil.

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) was applied for the determination of Rose water constituents. The effective parameters such as volume of extraction and disperser solvents, temperature, and salt effect were inspected by a full factorial design to identify important parameters and their interactions. It showed that salt addition had no effect on the efficiency. Next, a central composite design was applied to obtain optimum point of the important parameters. The optimal condition was obtained as 37.0 microL for extractor, 0.42 mL for disperser and temperature for 48 degrees C. The main components that were extracted at the optimum point were benzeneethanol (24.87%), geraniol (23.07%), beta-citronellol (22.38%), nerol (8.48%), eugenol (5.98%) and linalool (5.62%).

Preparation and application of magnetic graphene oxide coated with a modified chitosan pH-sensitive hydrogel: an efficient biocompatible adsorbent for catechin

In the present study, graft copolymerization of acrylic acid sodium salt (AAS) onto O-carboxymethyl chitosan (O-CMCs) produced a highly hydrophilic and pH-sensitive hydrogel polymer of O-CMCs-g-AAS with a porous surface morphology. The grafted chitosan copolymer was coated on magnetic graphene oxide (MGO) and characterized with TEM, SEM, and FT-IR techniques. The prepared nanocomposite, [O-CMCs-g-AAS]/MGO, was successfully used as an efficient and biocompatible adsorbent in magnetic solid phase extraction (MSPE) coupled with gas chromatography-mass spectrometry (GC-MS) for preconcentration and determination of catechin in tea beverages. The influence of the main parameters affecting the quality of the coating process was investigated and optimized using a response surface methodology. Under the optimum conditions, the adsorbent demonstrated a satisfactory adsorption capacity (27 mg g−1) for catechin and good linearity in the range of 0.005–5 μg mL−1 with a determination coefficient (R2) of 0.9987. The limit of detection (LOD) and limit of quantification (LOQ) were 0.001 and 0.003 μg mL−1, respectively. The relative standard deviation (RSD) was 4.1% (n = 5, C = 0.5 μg mL−1).

Optimization of dispersive liquid–liquid microextraction and improvement of detection limit of methyl tert-butyl ether in water with the aid of chemometrics

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry-selective ion monitoring (GC-MS-SIM) was applied to the determination of methyl tert-butyl ether (MTBE) in water samples. The effect of main parameters affecting the extraction efficiency was studied simultaneously. From selected parameters, volume of extraction solvent, volume of dispersive solvent, and salt concentration were optimized by means of experimental design. The statistical parameters of the derived model were R(2)=0.9987 and F=17.83. The optimal conditions were 42.0 μL for extraction solvent, 0.30 mL for disperser solvent and 5% (w/v) for sodium chloride. The calibration linear range was 0.001-370 μg L(-1). The improved detection limit with the aid of chemometrics was 0.3 ng L(-1). The relative standard deviation (RSD) with n=9 for 0.1 mg L(-1) MTBE in water with and without internal standard was 2.7% and 3.1%, respectively. Under the optimal conditions, the relative recoveries of spiked MTBE in different water samples were in the range of 100-105%.

Ligandless-ultrasound-assisted emulsification-microextraction combined with inductively coupled plasma-optical emission spectrometry for simultaneous determination of heavy metals in water samples

In the present study, the simple and efficient method of ligandless-ultrasound-assisted emulsification-microextraction (LL-USAEME) has been developed for the simultaneous preconcentration and determination of chromium and zinc in water samples by inductively coupled plasma-optical emission spectrometry (ICP-OES). Tetrachloroethylene was selected as the extraction solvent. A fractional factorial design (25−1) and a Box–Behnken design (BBD) were used to identify and optimize the most important parameters that influence the ultrasound microextraction process. The optimum levels of the effective parameters were: 190 μL for volume of extraction solvent, 11.4 for pH, 15% (w/v) for the salt concentration and 5 min for sonication time. Under the optimum conditions, the relative standard deviations (RSDs, C = 100 μg L−1, n = 7) were 2.5% and 3.1% for Cr and Zn respectively. The calibration graphs were linear in the range of 0.5–1500 μg L−1 for both the metal ions with determination coefficients (R2) of 0.997. The limits of detection (LODs) for Cr and Zn were 0.20 and 0.28 μg L−1, respectively. The proposed method was successfully applied to the analysis of three real environmental water samples and satisfactory recoveries (90–109%) were achieved.

Reactivity of disulfide bonds is markedly affected by structure and environment: implications for protein modification and stability

Disulfide bonds play a key role in stabilizing protein structures, with disruption strongly associated with loss of protein function and activity. Previous data have suggested that disulfides show only modest reactivity with oxidants. In the current study, we report kinetic data indicating that selected disulfides react extremely rapidly, with a variation of 104 in rate constants. Five-membered ring disulfides are particularly reactive compared with acyclic (linear) disulfides or six-membered rings. Particular disulfides in proteins also show enhanced reactivity. This variation occurs with multiple oxidants and is shown to arise from favorable electrostatic stabilization of the incipient positive charge on the sulfur reaction center by remote groups, or by the neighboring sulfur for conformations in which the orbitals are suitably aligned. Controlling these factors should allow the design of efficient scavengers and high-stability proteins. These data are consistent with selective oxidative damage to particular disulfides, including those in some proteins.

Ligandless-ultrasound-assisted emulsification microextraction followed by inductively coupled plasma-optical emission spectrometry for simultaneous determination of heavy metals in water samples

In this study, a simple and efficient method of ligandless-ultrasound-assisted emulsification microextraction (LL-USAEME) followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) has been developed for simultaneous extraction, preconcentration and determination of manganese, cadmium, cobalt and nickel in water samples. In the proposed approach, tetrachloroethylene was selected as extraction solvent. The effect of important experimental factors such as volume of extraction solvent, pH, sonication time, salt concentration, and temperature was investigated by using a fractional factorial design (25−1) to identify important factors and their interactions. In the next step, a Box-Behnken design (BBD) was applied for optimisation of significant factors. The obtained optimal conditions were: 30 µL for extraction solvent, 12 for pH, 5 min for sonication time, and 5% w/v for salt concentration. The limits of detections (LODs) for Cd(II), Co(II), Mn(II) and Ni(II) were 0.20, 0.13, 0.21 and 0.28 µg L−1, respectively. Relative standard deviations (RSD, C = 200.0 µg L−1, n = 9) were between 3.4–7.5% and the calibration graphs were linear in the range of 0.25 to 1000.0 µg L−1 for Mn, 0.5–1000.0 µg L−1 for Co and Ni and 1.0–250.0 µg L−1 for Cd. The determination coefficients (R 2) of the calibration curves for the analytes were in the range of 0.993 to 0.999. The proposed method was validated by using two certified reference materials, and also the method was applied successfully for the determination of heavy metals in different real water samples.

Magnetic removal of nitrate ions from aqueous solution using amino-silica coated magnetic nanoparticles modified by oxovanadium(IV) porphyrin

In this study, we have treated nitrate contaminated groundwater using modified magnetic nanoparticles. The modification of magnetite nanoparticles were conducted by 3-aminopropyl- triethoxysilane followed by oxovanadium(IV) porphyrin in order to enhance the removal of nitrate ions. Fourier Transform Infrared Spectroscopy (FT-IR),diffraction (XRD), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) were used to characterize the synthesized nanoparticles. The effect of pH, contact time, sorbent dosage and some co-existing anions present in aqueous solutions were investigated. The isothermal data of nitrate sorption conformed well to the Langmuir model and the maximum sorption capacity of nanosorbent for nitrate was 76.92 mg.g -1 . Thermodynamic study indicated that the adsorption is endothermic and spontaneous. Regeneration of nitrate adsorbed material could be be by NaOH and the modified magnetic nanoparticles exhibited good reusability.. proposed system can provide a fast and efficient removal of the nitrate ion by using just an external magnetic field. The competitive adsorption tests verified that, this system has good adsorption selectivity for nitrate ions.

Potent Anti-Cancer Effects of Less Polar Curcumin Analogues on Gastric Adenocarcinoma and Esophageal Squamous Cell Carcinoma Cells

Curcumin and its chalcone derivatives inhibit the growth of human cancer cells. It is reported that replacement of two OH groups in curcumin with less polar groups like methoxy increases its anti-proliferative activity. In this study, we explored benzylidine cyclohexanone derivatives with non-polar groups, to see if they possess increased anti-cancer activity. Novel 2,6-bis benzylidine cyclohexanone analogues of curcumin were synthesized, and their inhibitory effects on gastric adenocarcinoma (AGS) and esophageal squamous cell carcinoma (KYSE30) cancer cells were studied using an MTT assay. Cell apoptosis was detected by EB/AO staining, and cell cycle was analyzed by flow cytometry. Real-time PCR was performed for gene expression analysis. All synthesized analogues were cytotoxic toward gastric and esophageal cancer cells and showed lower IC50 values than curcumin. Treatment with 2,6-Bis-(3-methoxy-4-propoxy-benzylidene)-cyclohexanone (BM2) was 17 times more toxic than curcumin after 48 h incubation. All novel compounds were more effective than curcumin in apoptosis induction and cell cycle arrest at G1 phase. These results suggest that less polar analogues of curcumin have potent cytotoxicity in vitro. However, they need to be investigated further, especially with animal tumor models, to confirm their chemotherapeutic activity in vivo.

Efficient prediction of water vapor adsorption capacity in porous metal–organic framework materials: ANN and ANFIS modeling

Optimum design of water vapor separation process (dehumidification) using adsorption process mostly depends on the selection of appropriate porous materials or adsorbents with the highest equilibrium storage capacity of the vapor. Equilibrium capacity is generally evaluated through cost-demanding experiments via direct measurement of the vapor isotherm. Reliable prediction of the vapor adsorption capacity in porous materials provides a robust tool to a quick screening of porous materials appropriating for dehumidification process. In this article, adsorption capacity of water vapor in metal–organic framework (MOF) materials is predicted using two robust “artificial neural network (ANN)” and “Adaptive network-based fuzzy inference system (ANFIS)” methods. The three parameters of the surface area, pore volume and pore diameters are selected as input and the water vapor adsorption capacities of MOFs were computed as the output of the models. Comparison of the obtained results and real experimental data implied the superiority of the ANFIS and ANN models to predict the water vapor adsorption capacity into MOFs with a mean squared error (MSE) of 0.005 and 0.002, respectively. This clearly indicates a great potential for the application of both ANN and ANFIS methods to rapid screen MOFs suitable for water vapor adsorption.

Validation of a DEM Modeling of Gas-Solid Fluidized Bed using the S-statistic in the State-Space Domain

A reliable method was developed to validate results of a gas-solid bubble fluidized bed model with discrete element method (DEM) through comparison of corresponding pressure fluctuations experimental data. Attractors of two independent pressure signals, evaluation series of DEM model and reference time series of measured pressure signals, were compared in the state-space domain using the S-statistic. Comparison between two reconstructed attractors of evaluation and reference series was performed based on the null hypothesis. The null hypothesis that the evaluation and reference time series originate from the same dynamic sources is rejected if the two series significantly differ. To prove the power of the method, the S-statistic was estimated for obtained experimental data under the same operating conditions. In addition, experimental and model pressure fluctuations were decomposed into 9 levels using wavelet transform to study the validity of the model in a broad range of frequencies. Results indicated that the model results were consistent with experiments.