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In this work, an electromembrane extraction (EME) technique was used for the extraction and determination of gold from water samples prior to UV-Vis spectrophotometry. An artificial neural network (ANN) combined with imperialist competitive algorithm (ICA) has been applied to optimize the EME. The effective parameters including pH of acceptor phase, extraction time (t), volume of sample solution (V), stirring rate (S), and voltage (E) were chosen as input variables and the extraction recovery of gold was considered as output variable. The mean of squared error (i.e., 0.0009) and determination coefficient (i.e., 0.9821) were applied to estimate the performance of the ANN model. The limit of detection was 4.5 µg L−1(S/N = 3) on the optimized variables. The intra- and interday precisions (%) were found to be 6.7% and 2.6%, respectively. This technique was then applied for analysis of gold from environment water samples. [ABSTRACT FROM PUBLISHER]

The cover image, by Mostafa Khajeh et al, is based on the Original Article Extraction of caffeine and gallic acid from coffee by electrokinetic methods coupled with a hollow‐fiber membrane, DOI: 10.1111/jfpe.12565. [ABSTRACT FROM AUTHOR]

In this study the hollow fiber membrane coupled with electrokinetics was used, for the first time, for extraction and determination of caffeine and gallic acid from coffee prior to high performance liquid chromatography with photodiode array detection. Gallic acid (as an acid) and caffeine (as a base) were extracted from coffee at pH 5. In this work, several variables including applied voltage, coffee pH, acceptor phase pH, and extraction time were investigated. Our results showed that the extraction efficiency was increased when the applied voltage and extraction time were increased. The optimum conditions were pH 5 for the coffee, applied voltage of 20 V, and extraction time of 5 h. Gallic acid as an acid and caffeine as a base migrated to anode and cathode, respectively. Under the optimum conditions, gallic acid and caffeine were extracted with extraction efficiency of 21.3 and 23.4%, respectively. The intra-day and inter-day precisions (%) were found to be 7.6 and 4.8%, respectively. Therefore, this set-up for electrokinetics was potentially considered as a selective and simple preparation method for simultaneous extraction and analysis of basic and acid compounds in various matrices. Practical applications This study would benefit for extraction and separation of caffeine and gallic acid from coffee and other naturel samples. In this procedure, the new set-up for EKE based on two hollow fibers were employed for simultaneous removal of basic and acidic compounds. The EKE is used for extraction of organic compounds from food/soils with low permeability. The practical applications of this procedure have become extensive in a variety of fields, including electrokinetic waste remediation, biomaterials, radionuclides, and organic materials. [ABSTRACT FROM AUTHOR]

BACKGROUND A novel technique using maghemite nanoparticle-decorated hollow fibers to assist electromembrane extraction is proposed. Electromembrane extraction combined with dispersive liquid-liquid microextraction ( EME-DLLME) was applied for the extraction of thymol from Carum copticum, followed by gas chromatography with flame ionization detection ( GC-FID). RESULTS The use of maghemite nanoparticle-decorated hollow fibers was found to improve the extraction efficiency of thymol significantly. Important operational parameters, including pH of acceptor phase, extraction time, voltage and temperature, were investigated and optimized. At the optimal conditions, linearity in the range 4-1800 µg L−1 with a determination coefficient of 0.9996 was obtained. The limit of detection was 0.11 µg L−1 (S/N = 3) and the pre-concentration factor was 200. The intra- and inter-day precision was 5.9 and 2.2% respectively. The intra- and inter-day accuracy was higher than 93.6%. CONCLUSION The results indicated that EME-DLLME/ GC-FID is a useful technique for the extraction and determination of thymol in C copticum. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study, a hybrid of the artificial neural network-imperialist competitive algorithm (ANN-ICA) has been applied for prediction and optimization of the molecularly imprinted solid phase extraction method. This method has been used for the pre-concentration of methylene blue (MB) from environmental water samples prior to UV-Vis spectrophotometry. Molecular imprinted polymer sorbents were synthesized using radical polymerization by MB, 4-vinylpyridine, ethylene-glycol-dimethacrylate, 2,2′-azobisisobutyronitrile and methanol as a template, functional monomer, cross-linker, initiator, and porogen, respectively. The imprinted polymer was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The pH, adsorbent mass, adsorption time, eluent volume, and extraction time were been selected as input parameters and the recovery of MB was considered as an output variable of the ANN model. The results were then compared according to the performance function and determination coefficient. The Freundlich and Langmuir adsorption models were used to explain the isotherm constant. The maximum adsorption capacity was 417 mg g-1. At the optimized conditions, the limit of detection and relative standard deviation was found to be 0.31 μg l-1 and <1.7%, respectively. This method was applied to analysis the MB in various water samples. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a toxic element that can damage human organs. Determination of Cd in vegetables is often difficult because of low concentration and matrix effects. A simple, fast, flotation-assisted homogenous liquid–liquid microextraction (FA-HLLME) was developed for determination of Cd in vegetables prior to flame atomic absorption spectrometry (FAAS), in which 1-(2-pyridylazo)-2-naphthol (PAN) was used as a complexing agent. The process was carried out based on fast extraction of Cd from an acetic acid sample solution in which cyclohexane was the extracting solvent. Effects of pH, type and volume of extraction and homogeneous solvents, concentration of PAN, extraction time, and ionic strength on the extraction method were optimized. Under optimum conditions, the limit of detection and preconcentration factor were 0.6 µg·L−1and 38, respectively. The relative standard deviation was less than 3.1%. Extraction recovery was 94.3%–100.9%. [ABSTRACT FROM PUBLISHER]

Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography was applied for the extraction and determination of essential oil constituents of the Borago officinalis L. In this study, an experimental data-based artificial neural network (ANN) model was constructed to describe the performance of DLLME method for various operating conditions. The volume of extraction and dispersive solvents, extraction time and salt effect were the input variables of this process, whereas the extraction efficiency was the output. The ANN method was found to be capable of modeling this procedure accurately. The overall agreement between the experimental data and ANN predictions was satisfactory showing a determination coefficient of 0.982. The optimum operating conditionwas then determined by the genetic algorithm method. The optimal conditions were 248 μL volume of extraction solvent, 260 μL volume of dispersive solvent, 2.5 min extraction time and 0.16 mol L-1 of salt. The limit of detection and linear dynamic range were 0.15–24.0 and 1.2–1,800 ng mL-1, respectively. The main components of the essential oil were δ-cadinene (31.02%), carvacrol (24.91%), α-pinene (20.89%) and α-cadinol (16.47%). [ABSTRACT FROM AUTHOR]

Electromembrane extraction (EME) coupled with high-performance liquid chromatography was developed for determination of organic compounds including citric, tartaric and oxalic acid in biological samples. Organic compounds moved from aqueous samples, through a thin layer of 1-octanol immobilized in the pores of a porous handmade polypropylene tube, and into a basic aqueous acceptor solution present inside the lumen of the tube. This new set-up for EME has a future potential such as simple, cheap and fast sample preparation technique for extraction of organic compounds in various complicated matrices. The pH of acceptor phase, extraction time, voltage, ionic strength, temperature and stirring speed were studied and optimized. Optimum conditions were: the pH of acceptor phase, 7; extraction time, 30 min; voltage, 30 V and stirring speed, 500 rpm. At the optimum conditions, the preconcentration factors of 175–200, the limits of detection of 1.9-3.1 μg L-1 were obtained for the analytes. The developed procedure was then applied to the extraction and determination of organic acid compounds from biological samples. [ABSTRACT FROM AUTHOR]

In this study, the solid-phase tea waste procedure was used for separation, preconcentration and determination of uranium from water samples by UV-Vis spectrophotometer. In addition, Box-Behnken experimental design was employed to investigated the influence of six variables including pH, mass of adsorbent, eluent volume, amount of 1-(2-pyridylazo)-2-naphthol (PAN); and sample and eluent flow rates on the extraction of analyte. High determination coefficient ( R2) of 0.972 and adjusted- R2 of 0.943 showed the satisfactory adjustment of the polynomial regression model. This method was used for the extraction of uranium from real water samples. [ABSTRACT FROM AUTHOR]

In this study, dispersive solid phase extraction combined with dispersive liquid-liquid extraction has been developed for the extraction of benzene, toluene, ethylbenzene, and xylenes isomers (BTEX) in soil samples prior to gas chromatography-mass spectrometry. The BTEX were extracted from soil sample into acetonitrile by dispersive solid phase extraction method, and the extract was then used as dispersive solvent in dispersive liquid-liquid extraction procedure. Ant colony optimization-artificial neural network (ACO-ANN) has been employed to develop the model for simulation and optimization of this method. The volume of dispersive solvent, volume of extraction solvent, extraction time, and ultrasonic time were the input variables, while the multiple response function (Rm) of analytes was the output. The optimum operating condition was then determined by ant colony optimization method. At the optimum conditions, the limit of detections of 0.12-0.75 ng g−1 was obtained for the BTEX. The developed procedure was then applied to the extraction and determination of BTEX in the soil samples and one certified soil. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, chitosan-zinc oxide nanoparticles were used as a sorbent of miniaturized matrix solid-phase dispersion combined with flotation-assisted dispersive liquid-liquid microextraction for the simultaneous determination of 13 n-alkanes such as C8H18 and C20H42 in soil samples. The solid samples were directly blended with the chitosan nanoparticles in the solid-phase dispersion method. The eluent of solid-phase dispersion was applied as the dispersive solvent for the following flotation-assisted dispersive liquid-liquid microextraction for further purification and enrichment of the target compounds prior to gas chromatography with flame ionization detection. Under the optimum conditions, good linearity with correlation coefficients in the range 0.9991 < r2 < 0.9995 and low detection limits between 0.08 to 2.5 ng/g were achieved. The presented procedure combined the advantages of chitosan-zinc oxide nanoparticles, solid-phase dispersion and flotation-assisted dispersive liquid-liquid microextraction, and could be applied for the determination of n-alkanes in complicated soil samples with acceptable recoveries. [ABSTRACT FROM AUTHOR]

This work reports the preparation of molecularly imprinted polymer (MIP) particles for selective extraction and determination of aluminum ion from aqueous media. Polymerization was achieved in a glass tube containing AlCl3, morin, 4-vinylpyridine, ethyleneglycoldimethacrylate, 2,2' - azobisisobutyronitrile. The polymer block obtained was ground and sieved (55-75 μ m) and the Al (III)-morin complex was removed from polymer particles by leaching with 2 M of HCl, which leaves a cavity in the polymer particles. The polymer particles, both prior to and after leaching, have been characterized by IR and differential scanning calorimetry (DSC) studies. The effect of different parameters, such as pH, adsorption and desorption time, type and least amount of eluent for elution of complex from polymer were evaluated. Extraction efficiencies more than 99% were obtained by elution of the polymers with 15 mL of methanol-acetonitrile mixture (1:2) followed by ICP-OES. The limit of detection of the proposed method was 3.5 μ g L-1. A dynamic linear range (DLR) in the range of 20 to 200 μ g L-1 was obtained. The relative standard deviation (RSD) was less than 6.5%. The influence of various cationic and anionic interferences on percent recovery of complex was studied. The method was applied to the recovery and determination of aluminum in different real samples. [ABSTRACT FROM AUTHOR]

Firefly luciferase is a relatively unstable protein and commonly loses its activity at room temperature because of structural changes. The structural and functional stability of this protein is critical for its enzymatic applications. Different approaches are applied to increase the stability of this enzyme such as designing of covalent cross-links (disulfide bonds). In this study, luciferase mutants containing one or two disulfide bonds were compared to the native protein for their for their structural, thermodynamic, and functional properties. Mutant forms of P. Pyralis luciferase A²⁹⁶C-A³²⁶C and A²⁹⁶C-A³²⁶C/P⁴⁵¹C-V⁴⁶⁹C were used. Thermodynamic and biophysical studies were carried out using UV-Vis, fluorescence, circular dichroism, luminescence spectroscopy and differential scanning calorimetry (DSC). We observed that both mutant forms of the protein were more stable than the wild-type enzyme. However, the single disulfide bond containing mutant was structurally and functionally more stable than the mutant protein containing two disulfide bonds. Furthermore, the enzymatic activity of the single disulfide bond containing mutant protein was 7-folds greater than the wild type and the double disulfide bond proteins. The A²⁹⁶C-A³²⁶C mutation also increased the reversibility and disaggregation of the protein. The enhanced activity of the single disulfide bond mutant protein was contributed to the expansion of its active site cleft, which was confirmed by bioinformatics tools.

A novel peroxidase-like artificial enzyme, named "caseoperoxidase", was biomimetically designed using a nano artificial amino acid apo-protein hydrophobic pocket. This four-component nano artificial enzyme containing heme-imidazole-β-casein-SDS exhibited high activity growth and k(cat) performance toward the native horseradish peroxidase demonstrated by the steady state kinetics using UV-vis spectrophotometry. The hydrophobicity and secondary structure of the caseoperoxidase were studied by ANS fluorescence and circular dichroism spectroscopy. Camel β-casein (Cβ-casein) was selected as an appropriate apo-protein for the heme active site because of its innate flexibility and exalted hydrophobicity. This selection was confirmed by homology modeling method. Heme docking into the newly obtained Cβ-casein structure indicated one heme was mainly incorporated with Cβ-casein. The presence of a main electrostatic site for the active site in the Cβ-casein was also confirmed by experimental methods through Wyman binding potential and isothermal titration calorimetry. The existence of Cβ-casein protein in this biocatalyst lowered the suicide inactivation and provided a suitable protective role for the heme active-site. Additional experiments confirmed the retention of caseoperoxidase structure and function as an artificial enzyme.