Ghodratollah Absalan

Shiraz University, Chimaz, Fārs, Iran

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Publications (53)122.83 Total impact

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    ABSTRACT: Coupling of temperature-controlled ionic liquid-based dispersive liquid phase microextraction (TCIL-DLPME) with reflection scanometry for quantitative determination of colored species in solution is introduced for the first time. To evaluate the performance and applicability of the methodology, the ferrous ion which forms a red complex with 2,2′-bipyridyl (bipy) was used as the model analyte. The ionic liquid (IL) 1-hexyl-3-methylimidazolium hexafluorophosphate was used for extracting the complex by TCIL-DLPME after diluting the IL phase with dimethylformamide, which was injected into the detection chamber in a Plexiglas® sheet. It was scanned with a conventional flatbed-scanner. The color of the image was analyzed for its R (red), G (green), and B (blue) components using Adobe Photoshop software. Optimization of the parameters affecting the extraction process as well as the calibration curve was based on the G (green) color value as the analytical signal. Some essential parameters including the IL chemical structure, volume of IL, bipy concentration, pH, temperature, centrifugation time, and aqueous phase volume have been studied in detail. Under optimum experimental conditions the method was successfully applied for the determination of Fe(II) in iron supplement oral drop (IroVit) and boiler water samples.
    No preview · Article · Dec 2015 · Analytical methods
  • Ghodratollah Absalan · Morteza Akhond · Mahvash Soleimani · Hamid Ershadifar
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    ABSTRACT: Palladium nanoparticles (PdNPs) were electrodeposited on the carbon ionic liquid electrode (CILE) for evaluating the assemblage for electrochemical determination of isoniazid (INH). The surface morphological investigation of the fabricated electrode by using scanning electron microscopy indicated efficient electrodeposition of PdNPs with the particle diameter of 30–100 nm when a constant potential of − 0.2 V for duration of 60 s was applied. Electrocatalytic oxidation of isoniazid at this electrode was investigated in phosphate buffer solution (pH 7.0) using cyclic voltammetry. A highly reproducible and well-defined peak with a high electrocatalytic peak current was obtained for INH at a low overpotential of + 0.34 V versus Ag/AgCl. Under optimized experimental conditions, linear relationship between anodic peak current and INH concentration in the ranges of 5.0 × 10− 6–1.0 × 10− 4 and 1.5 × 10− 4–2.6 × 10− 3 mol L− 1 INH with a detection limit of 4.7 × 10− 7 mol L− 1 was obtained. The procedure was successfully applied for analysis of INH in human blood serum and pharmaceutical samples.
    No preview · Article · Dec 2015
  • Ghodratollah Absalan · Morteza Akhond · Hamid Ershadifar · Mohammad Ali Rezaei
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    ABSTRACT: Efficient preparation of stable gold nanoparticles in an organic solvent has been studied. To do this, two approaches have been performed. In the first approach, AuCl4- and sodium borohydride were used, respectively, as precursor and reducing agent in the presence of ionic liquid 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) as the capping agent in the aqueous phase. Extraction into different organic solvents showed that the phase transfer efficiency of the gold nanoparticles into chloroform was higher than dichloromethane, toluene and n-heptane. The nanoparticles were stable in chloroform for more than three months. The effect of different experimental conditions on phase transfer efficiency of the nanoparticles has been checked by UV-vis spectroscopy, dynamic light scattering and transmission electron microscopy. In the second approach, the complex of [C12mim]Br with AuCl4-, after formation in aqueous phase (upper phase), was extracted into chloroform. Sodium borohydride solution was injected into the aqueous phase followed by vigorous stirring. The result was production of dispersed gold nanoparticles in the chloroform phase through reduction of the extracted complex by sodium borohydride. Both approaches were compared with each other in terms of reproducibility, procedure time, nanoparticles size and effect of ionic liquid. A solution of gold nanoparticles in chloroform (prepared by the second approach) was brought into contact with either cysteine or homocysteine aqueous solution in order to form a thin film of the gold nanoparticles at the water/chloroform interface.
    No preview · Article · Sep 2015 · Colloids and Surfaces A Physicochemical and Engineering Aspects
  • Mina Solhtalab · Hamid Reza Karbalaei-Heidari · Ghodratollah Absalan
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    ABSTRACT: Ionic liquids (ILs) are considered as green alternatives to organic solvents in various enzymatic biotechnological processes. A wide variety of hydrophilic and hydrophobic ionic liquids have been synthesized in order to investigate their effects on both enzyme activity and stability. In most cases, hydrophobic ILs such as those containing PF6- anion have shown better performances in enzymatic reactions. In the present work, the effect of alkyl chain length of [CnMIM][Br] (n = 2, 4, 6, 12) on hydrolytic activity of Thermoanaerobacter thermohydrosulfuricus lipase (TTL), as a model enzyme, was evaluated and compared with [C4MIM][PF6] as a hydrophobic ionic liquid. Moreover, effect of hydrophilic ILs on the activity and thermal stability of TTL in different concentrations of ionic liquids was studied. The results showed that TTL had the highest lipase activity in the presence of 0.3 M [C2MIM][Br], 1 M [C4MIM][Br] and 0.3 M [C6MIM][Br]. However, no significant effect was revealed in the presence of [C12MIM][Br]. A comparison between the effects of [C4MIM][PF6] and [C4MIM][Br] on the TTL thermostability at 85°C and 90°C revealed that the hydrophobic anion PF6- provided a good stabilizing effect for TTL; although the influence of hydrophilic functions is also promising. According to the findings, it could be concluded that the TTL and probably similar enzymes can be used for several biotransformation reactions by tuning the hydrophilic ionic liquids concentrations as solvents.
    No preview · Article · Sep 2015 · Journal of Molecular Catalysis B Enzymatic
  • Ghodratollah Absalan · Morteza Akhond · Hamid Ershadifar
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    ABSTRACT: Carbon ionic liquid electrode (CILE) was used as a substrate for immobilization and determination of amoxicillin (AMX) in phosphate buffer solution. The electrochemical response of AMX showed an irreversible oxidation peak in the first scan and redox peaks corresponding to the electrooxidation of product in the subsequent scans which gradually grew upon repetitive scanning. Effect of experimental conditions on electrooxidation of AMX and its adsorbed intermediates was investigated, and possible mechanism for strong immobilization is suggested. The electrode response was linear in the concentration range of 5.0 to 400.0 μmol L−1 AMX with a detection limit of 0.8 μmol L−1 AMX. There was no serious interference from other β-lactam family of antibiotics such as ampicillin and penicillin. The electrode showed good selectivity as well as high sensitivity toward quantification of AMX in pharmaceuticals and urine samples.
    No preview · Article · Aug 2015 · Journal of Solid State Electrochemistry
  • Javad Tashkhourian · Ghodratollah Absalan · Marzieh Jafari · Saber Zare
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    ABSTRACT: A rapid, simple and inexpensive spectrofluorimetric sensor for determination of doxycycline based on its interaction with thioglycolic acid-capped cadmium telluride quantum dots (TGA/CdTe QDs) has been developed. Under the optimum experimental conditions, the sensor exhibited a fast response time of <10s. The results revealed that doxycycline could quench the fluorescence of TGA/CdTe QDs via electron transfer from the QDs to doxycycline through a dynamic quenching mechanism. The sensor permitted determination of doxycycline in a concentration range of 1.9×10(-6)-6.1×10(-5)molL(-1) with a detection limit of 1.1×10(-7)molL(-1). The sensor was applied for determination of doxycycline in honey and human serum samples. Copyright © 2015 Elsevier B.V. All rights reserved.
    No preview · Article · Jul 2015 · Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy
  • Sedigheh Kamran · Ghodratollah Absalan · Mozaffar Asadi
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    ABSTRACT: In this paper, nanoparticles of Fe3O4 as well as their modified forms with different ionic liquids (IL-Fe3O4) were prepared and used for adsorption of lysozyme. The mean size and the surface morphology of the nanoparticles were characterized by TEM, XRD and FTIR techniques. Adsorption studies of lysozyme were performed under different experimental conditions in batch system on different modified magnetic nanoparticles such as, lysozyme concentration, pH of the solution, and contact time. Experimental results were obtained under the optimum operational conditions of pH 9.0 and a contact time of 10 min when initial protein concentrations of 0.05-2.0 mg mL(-1) were used. The isotherm evaluations revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The maximum obtained adsorption capacities were 370.4, 400.0 500.0 and 526.3 mg of lysozyme for adsorption onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br] per gram of adsorbent, respectively. The Langmuir adsorption constants were 0.004, 0.019, 0.024 and 0.012 L mg(-1) for adsorptions of lysozyme onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br], respectively. The adsorption capacity of lysozyme was found to be dependent on its chemical structure, pH of the solution, temperature and type of ionic liquid as modifier. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated. Furthermore, the thermodynamic parameters were calculated. Protein could desorb from IL-Fe3O4 nanoparticles by using NaCl solution at pH 9.5 and was reused.
    No preview · Article · Jul 2015 · Amino Acids
  • Ghodratollah Absalan · Morteza Akhond · Asma Bananejad · Hamid Ershadifar
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    ABSTRACT: A carbon ionic liquid electrode modified with Fe3O4 magnetic nanoparticle (Fe3O4NPs/CILE) was employed for nitrite determination by cyclic voltammetry. The results showed that the Fe3O4NPs/CILE exhibited a significant improvement in the oxidation peak current of nitrite. After optimizing the operational conditions, a linear response range from 10 to 900 µmol L−1 with a low detection limit of 0.70 µmol L−1 was obtained. The proposed sensor was stable with a sensitivity of 0.0402 μA μmol−1 L and good repeatability evaluated in terms of relative standard deviation (RSD n = 6). Possible interferences from several coexisting ions were evaluated. The sensor was applied for voltammetric determination of nitrite in some real samples. The results were consistent with those obtained with the standard spectrophotometric procedure.
    No preview · Article · Jul 2015 · Journal of the Iranian Chemical Society
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    ABSTRACT: A novel kinetic spectrophotometric method is developed for determination of ampicillin. The method is based on aggregation of gold nanoparticles in a chemical process that involved decomposition of ampicillin catalyzed by cadmium ion in methanol as solvent. The optimum experimental conditions for determination of ampicillin were established. The method permitted determination of ampicillin in a concentration range of 16.0–96.0 µg ml−1 with a detection limit of 13.0 µg ml−1. The interferences of the species which are mostly available in biological samples were not significant in determination of ampicillin. The method is simple and sensitive for analyzing of ampicillin and is applicable for its assay in pharmaceutical formulations.
    No preview · Article · May 2015 · Journal of the Iranian Chemical Society
  • Morteza Akhond · Ghodratollah Absalan · Hamid Ershadifar
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    ABSTRACT: A novel, simple and highly sensitive colorimetric method is developed for determination of Amoxicillin (AMX). The system is based on aggregation of citrate-capped gold nanoparticles (AuNP) in acetate buffer (pH=4.5) in the presence of the degradation product of Amoxicillin (DPAMX). It was found that the color of gold nanoparticles changed from red to purple and the intensity of surface plasmon resonance (SPR) peak of AuNPs decreased. A new absorption band was appeared in the wavelength range of 600-700nm upon addition of DPAMX. The absorbance ratio at the wavelength of 660 and 525nm (A660/A525) was chosen as the analytical signal indirectly related to AMX concentration. The linearity of the calibration graph was found over the concentration range of 0.3-4.5μM AMX with a correlation coefficient of 0.9967. Under the optimum experimental conditions, the detection limit was found to be 0.15μM. The applicability of the method was successfully demonstrated by analysis of AMX in pharmaceutical formulations including capsules and oral suspensions. Copyright © 2015 Elsevier B.V. All rights reserved.
    No preview · Article · Feb 2015 · Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy
  • Ghodratollah Absalan · Morteza Akhond · Hamid Ershadifar
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    ABSTRACT: A new application of a carbon ionic liquid electrode (CILE) has been explored for preconcentration and quantification of trace amount of Au(III) chlorocomplexes. The procedure is based on the accumulation of tetrachloroaurate complexes at the electrode surface under an open circuit potential condition followed by cyclic voltammetry (CV) and differential pulse cathodic stripping voltammetry (DPCSV). An ion exchange mechanism has been proposed for efficient and fast accumulation of Au(III) chlorocomplexes. Effects of different experimental parameters such as electrolyte concentration, pH, and preconcentration time on the voltammetric signals were investigated. It was found that under the optimized experimental conditions, the linear range of measurement and the detection limit were 5.00 × 10−9–2.25 × 10−6 and 0.80 × 10−9 mol L−1, respectively. Possible interference from coexisting ions was also studied. The procedure was applied for determination of gold in water and human blood serum samples, and acceptable accuracy was achieved.
    No preview · Article · Jan 2015 · Journal of Solid State Electrochemistry
  • Ghodratollah Absalan · Morteza Akhond · Elmira Rafatmah · Yousef Alipour
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    ABSTRACT: Gold nanoparticles (AuNPs) and L-cysteine (L-cys), in order, as first and second layer were coated on the surface of a commercial thin-layer chromatography (TLC) plate. This assemble has been used as a new substrate for direct resolution of propranolol enantiomers based on the ordinary TLC technique. The effect of concentrations of the involved chemicals, time periods of the required processes, pH of the sample solutions, as well as the effects of different coating protocols on the resolution of the enantiomers, were investigated in order to find the optimized separation conditions. The results showed that 10.0 mM copper(II) acetate, in 70% ethanol-water adjusted at pH = 6.3, was suitable for being used as the mobile phase. The AuNPs with the average size of 15 nm and L-cys solution with a concentration of 10.0 mM and pH = 8.1 had been chosen for impregnating TLC plates.
    No preview · Article · Dec 2014 · JPC - Journal of Planar Chromatography - Modern TLC
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    Maryam Ghaemi · Ghodratollah Absalan · Leila Sheikhian
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    ABSTRACT: This paper assesses the adsorption characteristics of Titan yellow and Congo red on CoFe2O4 magnetic nanoparticles. The adsorption behavior of Titan yellow and Congo red from aqueous solution onto CoFe2O4 magnetic nanoparticles has been determined by investigating the effects of pH, concentration of the dye, amount of adsorbent, contact time, ionic strength and temperature. Experimental results indicated that CoFe2O4 nanoparticles can remove more than 98 % of each dye under optimum operational conditions of a dosage of 15.0 mg CoFe2O4, pH 3.0, initial dye concentration of 22–140 mg L−1, and contact times of 2.0 and 15.0 min for Congo red and Titan yellow, respectively. Langmuir and Freundlich isotherm models have been used to evaluate the ongoing adsorption kinetic equations. Regeneration of the saturated adsorbent was possible by NaCl/acetone solution as eluent. The maximum adsorption capacities were 200.0 and 212.8 mg dye per gram adsorbent for Congo red and Titan yellow, respectively. With the help of adsorption isotherm, thermodynamic parameters such as free energy, enthalpy and entropy have been calculated. On the basis of pseudo-first-order and pseudo-second-order kinetic equations, different kinetic parameters have been obtained.
    Full-text · Article · Dec 2014 · Journal of the Iranian Chemical Society
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    Bahram Hemmateenejad · Mohsen Nekoeinia · Ghodratollah Absalan · Mehdi Ansari
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    ABSTRACT: Nystatin, one of the tetraene antifungal antibiotics, is very sensitive to light. Thus, when nystatin is exposed to natural daylight, it is photodegraded to products of lower biological activity. In this work, the photodegradation kinetics of nystatin was monitored by a UV-Vis spectrophotometry method. The absorbance spectra of the nystatin, exposed to a 366 nm UV lamp, were recorded at different periods of time. By application of factor analysis to the absorbance data matrix, three absorbing chemical species, coexisting in the reaction system, were detected. The soft-modeling multivariate curve resolution-alternating least squares analysis of the evolutionary absorbance data revealed that nystatin undergoes photodegradation in a two-step consecutive manner. Hard-modeling data analysis suggested that reaction has first-order kinetics in the first step and zero-order kinetics in the second step. The reaction rate constants of the first and second steps were estimated as 0.0929 (±0.0076) and 0.0052 (±0.0016)/min, respectively. Finally, the pure spectra of the resolved chemical species were calculated.
    Full-text · Article · Aug 2014 · Journal of AOAC International
  • Shokoufeh Ahmadi · Ghodratollah Absalan · Douglas Craig · Douglas Goltz
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    ABSTRACT: Purpurin is an anthraquinone dye that is found in plant material such as Madder root. The separation of purpurin using capillary electrophoresis under alkaline condition can be complicated by reproducibility in peak height and peak shape. In this study the poor peak reproducibility of capillary electrophoresis separations was attributed to photochemical properties of purpurin. Experiments were carried out using UV visible and fluorescence spectrophotometry to measure the 1st order rate constant for the photochemical fading of purpurin. At pH = 9.24 the rate constant was 4.5 x 10(-3) s(-1) and at pH = 7.0 the rate constant was determined to be 5.0 x 10(-5) s(-1). Proton NMR, thin layer chromatography, gas chromatography and UV visible spectrophotometry techniques were also employed to identify the photo-degraded products of purpurin. (c) 2014 Elsevier Ltd. All rights reserved.
    No preview · Article · Jun 2014 · Dyes and Pigments
  • Sedigheh Kamran · Mozaffar Asadi · Ghodratollah Absalan
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    ABSTRACT: In this paper, nanoparticles of Fe3O4 as well as its binary mixtures with ionic liquid 1-hexyl-3-methylimidazolium bromide (IL-Fe3O4) were prepared and used for adsorption of folic acid, riboflavin and ascorbic acid. The mean size and the surface morphology of both nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy techniques. The pH of the point of zero charge (pHpzc) of both Fe3O4 and IL-Fe3O4 were obtained based on the experimental curves corresponding to the immersion technique. Experimental results were obtained under the optimum operational conditions of: 40 mg of nanoparticle and contact time of 10 minutes with an initial concentration of the vitamins of 20 mg L−1. The isotherm evaluations revealed that the Freundlich model attained better fits to the equilibrium data than the Dubinin-Radushkevich model. The maximum obtained adsorption capacities of folic acid, riboflavin and ascorbic acid were 22.5, 4.8 and 6.9 mg per gram of adsorbent, respectively. The adsorption capacities of the vitamins were found to be dependent on their chemical structures, pH of the solution and temperature. The applicability of pseudo-first order and pseudo-second order kinetic models was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium adsorption capacity and correlation coefficients. Furthermore, both adsorption processes of folic acid and ascorbic acid were endothermic and vitamins could be desorbed from IL-Fe3O4 nanoparticles by using NaCl solution at pH 3.0 for recycling the nanoparticles.
    No preview · Article · Feb 2014 · Analytical methods
  • Ghodratollah Absalan · Maryam Arabi · Reza Khalifeh · Hashem Sharghi · Javad Tashkhourian
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    ABSTRACT: A coated wire Fe2+ ion selective electrode based on laboratory-synthesized crown ether, as a neutral carrier, was constructed. The effects of different experimental parameters such as the amount of plasticizer, the amount of ionophore, pH of the sample solution, and coexisting ions on the potentiometric responses of the electrode were investigated. The electrode exhibited a Nernstian slope of 29.20 +/- 0.87 mV/decade over a wide concentration range of 7.2 x 10(-7) - 6.9 x 10(-3) M Fe2+. The potentiometric responses were independent of the pH of the test solution in the pH range of 4.6-9.6. The response time and detection limit were found to be 3.0 min and 6.7 x 10(-7) M, respectively. The electrode revealed good selectivity for Fe2+ in the presence of different coexisting cations and anions. It was certified as an indicator electrode by performing a potentiometric titration for a standard sample of Fe2+ ion.
    No preview · Article · Feb 2014 · IEEE Sensors Journal
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    Maryam Ghaemi · Ghodratollah Absalan
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    ABSTRACT: We have investigated the adsorption of herring sperm DNA on Fe3O4 magnetic nanoparticles (NPs) before and after modification with the ionic liquid 1-hexyl-3-methylimidazolium bromide. Experiments were performed in a batch mode, and the effects of DNA concentration, pH of the sample solution, ionic strength, temperature, and contact time between reagents were optimized. An evaluation of the adsorption isotherm revealed that the Langmuir model better fits the equilibrium data than the Freundlich model. The maximum adsorption capacities of the unmodified and modified NPs, respectively, were found to be 11.8 and 19.8 mg DNA per gram of adsorbent. The adsorption of DNA onto the modified NPs was endothermic, while it was exothermic in the case of the unmodified NPs. The DNA can be desorbed from the modified surfaces of the NPs by using EDTA as the eluent. The NPs were able to adsorb about 90 ± 1.5 % of DNA after being recycled for three times. The method is simple, fast, robust, and does not require organic solvents or sophisticated equipment. Figure Fe3O4 nanoparticles as well as 1-hexyl-3-methylimidazolium bromidecoated Fe3O4 nanoparticles were prepared and used for adsorption of DNA. The mean size and the surface morphology of both nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. The correlation coefficient of the Langmuir model suggests a better fit for the experimental equilibrium adsorption data.
    Full-text · Article · Jan 2014 · Microchimica Acta
  • Maryam Ghaemi · Ghodratollah Absalan
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    ABSTRACT: Adsorption characteristics and doxycycline (DC) removal efficiency of Fe3O4 magnetic nanoparticles as adsorbents have been determined by investigating the effects of pH, concentration of the DC, amount of adsorbents, contact time, ionic strength and temperature. The mechanism of adsorption was also studied. The adsorption of DC to the Fe3O4 magnetic nanoparticles could be described by Langmuir-type adsorption isotherms. Short contact time between the reagents, reusability of Fe3O4 for three times after recycling of the nanoparticles, good precision and accuracy, wide working pH range and high breakthrough volume are among the highlights of this procedure. The proposed extraction and determination procedure based on magnetic nanoparticles as adsorbent was successfully applied to the determination of DC spiked in honey and various water samples. The method presented here is fast, simple, cheap and robust, and it does not require the use of organic solvents. Also, the method needs only a magnet and can be performed in any laboratory without sophisticated equipment.
    No preview · Article · Jan 2014 · Journal of the Iranian Chemical Society
  • Leila Sheikhian · Morteza Akhond · Ghodratollah Absalan · Douglas M. Goltz
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    ABSTRACT: The partitioning behavior of model acidic (bovine serum albumin, BSA), basic (hen egg white lysozyme, LYS), and neutral (horse heart myoglobin, MYO) proteins in ionic liquid-based aqueous biphasic systems containing Reactive Red-120 dye has been reported. This study found that partition coefficients of the proteins depended on their chemical structures, pH of the aqueous phase, temperature, and composition of the aqueous biphasic system. It was found that partition coefficients of proteins in aqueous biphasic system containing RR-120 were in the order of LYS > MYO > BSA. Recovery of the hydrophilic ionic liquid, [C4mim]Br, was achieved by using hydrophobic ionic liquid, [C4mim]PF6.
    No preview · Article · Oct 2013 · Separation Science and Technology