[Show abstract][Hide abstract] 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.
Journal of the Iranian Chemical Society 12/2014; 11(6). · 1.47 Impact Factor
[Show abstract][Hide abstract] 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.
Journal of AOAC International 08/2014; 97(4). · 1.23 Impact Factor
[Show abstract][Hide abstract] 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. FigureFe3O4 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.
[Show abstract][Hide abstract] ABSTRACT: A novel methodology for analysis of enantiomer composition of chiral compounds based on measuring of their critical micelle concentration by using spectrophotometric technique is introduced. The proposed method does not require any chiral selector and the corresponding process is simple, fast, reproducible, and inexpensive. The procedure was successfully applied for analysis of naproxen. The critical micelle concentration data showed that (R)-naproxen could be determined with an RSD of 1.1% and a relative error of -5.6% when a real sample containing the racemic mixture of naproxen with a total concentration of 0.04mM was tested.
Journal of pharmaceutical and biomedical analysis 04/2013; 83C:96-100. · 2.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An extracellular protease was purified from a novel moderately halophilic bacterium Salinivibrio sp. strain MS-7 by the combination of an acetone precipitation (40-80 %) step and a DEAE-cellulose anion exchange column chromatography. Kinetic parameters of the enzyme exhibited V max and K m of 130 U/mg and 1.14 mg/ml, respectively, using casein as a substrate. The biochemical properties of the enzyme revealed that the 21-kDa protease had a temperature and pH optimum of 50 °C and 8.0, respectively. The enzyme was strongly inhibited by phenylmethylsulfonyl fluoride, Pefabloc SC, chymostatin, and also EDTA, indicating that it belongs to the class of serine metalloproteases. Interestingly, Ba(2+) and Ca(2+) (2 mM) strongly enhanced the enzyme activity, while Fe(2+) and Mg(2+) activated moderately and Zn(2+), Ni(2+), and Hg(2+) decreased the enzyme activity. The effect of organic solvents with different logP on the purified protease revealed complete stability in toluene, ethyl acetate, chloroform, and n-hexane at 10 and 50 % (v/v) and moderate stability even in 50 % of DMSO and ethanol. The behavior of the MS-7 protease in three imidazolium-based ionic liquids exhibited suitable activity in these green solvent systems, especially in 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]). Comparison of the purified protease with other previously reported proteases suggests that strain MS-7 secrets a novel organic solvent-tolerant protease with outstanding activity in organic solvents and imidazolium-based ionic liquids, which could be applied in low water synthetic section of industrial biotechnology.
Applied biochemistry and biotechnology 04/2013; · 1.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper partitioning behaviors of reactive red-120, 4-(2-pyridylazo)-resorcinol, and methyl orange as model azo dyes in ionic liquid-based aqueous biphasic systems were studied. For designing aqueous biphasic systems and investigating the partitioning of the model dyes, phase diagrams and binodal curves were obtained at 25 °C for [C4mim][Br]/salt systems at different pH values. It was found that the partition coefficients of the studied dyes depended on their chemical structures, pH of the aqueous phase, temperature and composition of the aqueous biphasic system. Ionic liquid-based aqueous biphasic extraction was an efficient and suitable method for partitioning of dyes into ionic liquid-rich top phase. Efficient extraction of dyes into IL phase was done within 1 min. The hydrophilic ionic liquid 1-butyl-3-methylimidazolium bromide, [C4mim][Br], in top phase was efficiently recovered by using the hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim][PF6]. In the recycling process, almost no dye was extracted into [C4mim][PF6] phase.
Journal of Environmental Chemical Engineering 01/2013;
[Show abstract][Hide abstract] 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.
Separation Science and Technology 01/2013; 48(15). · 1.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: New complexes of Co(II), Ni(II), Cu(II) and Zn(II) with four new tetraaza Schiff base ligands, N,N′-bis(2-quinolylmethylidene)-1,2-ethanediimino (L1), N,N′-bis(2-quinolylmethylidene)-1,2-propanediimino (L2), N,N′-bis(2-quinolylmethylidene)-1,3-propanediimino (L3), N,N′-bis(2-quinolylmethylidene)-4-nitro-1,2-phenylenediimine (L4), were synthesized and characterized by elemental analysis, IR, 1H NMR, and UV-Vis spectroscopy. The thermodynamic formation constants of the complexes were measured spectrophotometrically, at the constant ionic strength 0.1 M (NaClO4), at 25 °C in MeOH solvent. The trend of the complex formation of a given metal ion with the ligands was found to be as follows L2 > L1 > L3 > L4 and the trend of a given ligand with the metal ions was Co(II) > Ni(II) > Cu(II) > Zn(II).
Journal of the Iranian Chemical Society 12/2012; 8(4). · 1.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Many chiral selectors have been used for recognition of enantiomeric compounds but their synthesis involves time-consuming and expensive multistep-processes with almost not optically pure products. In this paper, 1-butyl-3-methylimidazolium (T-4)-bis[(αS)-α-(hydroxy-O) benzeneacetato-κO] borate, a chiral ionic liquid which can be easily synthesized, was first used as a chiral selector in solution. The enantiomer compositions of propranolol hydrochloride were determined by using this chiral selector and the spectrophotometric method. The data of UV spectra showed that S-propranolol hydrochloride could be recognized in the mixture of the enantiomers with a total concentration of 1.50 × 10−4 M.
[Show abstract][Hide abstract] ABSTRACT: In this paper, adsorption behaviors of typical neutral (alanine), acidic (glutamic acid) and basic (lysine) amino acids onto the surfaces of neutral as well as positively and negatively charged silver chloride nanoparticles were examined. Silver chloride nanoparticles with different charges and different water content were synthesized by reverse micelle method. The adsorptions of the above mentioned amino acids onto the surfaces of differently charged silver chloride nanoparticles were found to depend strongly on various parameters including pH of the aqueous solution, type of amino acid, water to surfactant mole ratio, and type of charges on the surfaces of silver chloride nanoparticles. It was found that the interaction of -NH(3) (+) groups of the amino acids with silver ion could be a driving force for adsorption of amino acids. Alanine and Glutamic acid showed almost similar trend for being adsorbed on the surface of silver chloride nanoparticles. Electrostatic interaction, hydrophobicity of both nanoparticle and amino acid, complex formation between amine group and silver ion, interaction between protonated amine and silver ion as well as the number of nanoparticles per unit volume of solution were considered for interpreting the observed results.
[Show abstract][Hide abstract] ABSTRACT: An optode was designed for an indirect determination of ascorbic acid by using neocuproine, which has been coated on transparent triacetylcellulose film as a membrane. The proposed method is based on the oxidation of ascorbic acid to dehydroascorbic acid with the Cu(II) and neocuproine reagent. The increase in the absorbance value of the optode at the maximum wavelength of 455 nm was related to the ascorbic acid concentration in aqueous samples. The sensitivity of the method was improved by using room-temperature ionic liquid, [C(8)MIM][PF(6)]. The linear dynamic range for the determination of ascorbic acid was 7.4 × 10(-5) - 3.5 × 10(-3) mol L(-1) with a limit of detection of 2.2 × 10(-5) mol L(-1) (n = 10) and a response time range of 6.0 - 8.0 min. The optode was successfully applied for the determination of ascorbic acid in orange juice.
[Show abstract][Hide abstract] ABSTRACT: The nanoparticles of Fe(3)O(4) as well as the binary nanoparticles of ionic liquid and Fe(3)O(4) (IL-Fe(3)O(4)) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe(3)O(4) nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60mg, a pH of 2.5, and a contact time of 2min when initial dyes concentrations of 10-200mg L(-1) were used. The maximum adsorption capacity of IL-Fe(3)O(4) was 166.67 and 49.26mg g(-1) for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62L mg(-1) for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe(3)O(4) by using a mixed NaCl-acetone solution and adsorbent was reusable.
Journal of hazardous materials 05/2011; 192(2):476-84. · 4.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this article, the ability of a new and efficient hard-soft method, previously proposed by our research group, is reported for modeling of the complex formation equilibria in the presence of interferences. This method is based on the net analyte signal (NAS) concept, which is a part of total signal that is directly related to the concentration of the component of interest. It monitors the concentration changes of any chemical species involved in the evolutionary process without requiring any pure spectra or having previous knowledge about the presence of the interferences. The proposed hard-soft method based on net analyte signal (HS-NAS) only needs a chemical model for one of the species involved in the reaction under study. The reliability of the method was examined by applying it to the measured data and spectrum of the known real systems of Fe(2+)-azithromycin and Ca(2+)-tetracycline.
[Show abstract][Hide abstract] ABSTRACT: Rank deficiency is the major problem associated with the chemometrics modeling of the second-order chemical reactions of the form of A+B→C. In this article, the application of the hard-soft-net analyte signal (HS-NAS), as a newly proposed method in our research group, is described for modeling of second-order reactions. This combined hard-soft method is based on the net analyte signal (NAS) concept, which is defined as a part of total signal that is directly related to the concentration of the component of interest. Therefore, concentration changes versus time can be obtained by calculating NAS for any chemical species involved in the reaction without requiring any pure component spectra or extra runs. The power of the method was verified by applying it to the resolution of simulated data sets containing noises added at different levels. The resolution of the second-order reaction between amoxicillin and 1, 2-naphthoqoinone was also tested as a real chemical system.
Chemometrics and Intelligent Laboratory Systems 05/2010; 102(1):35-44. · 2.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new cyanide optode was designed using [N,N′-bis(salicyliden)-2,3-diaminopyridine]tributylphosphine cobalt(III) percholorate monohydrate complex, which was coated on transparent triacetylcellulose film as membrane. The reduction in the absorbance value of the optode at the maximum wavelength of 380nm was related to cyanide concentration in aqueous samples. The sensitivity of the method was improved by using room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, [C4MIM][PF6], introduced in constructing the optode membrane. The linear dynamic range for the determination of cyanide was 1.0×10−5 to 2.5×10−4M with a limit of detection of 4.2×10−6M (n=10) and a response time range of 7–10min. The optode was successfully applied for the determination of cyanide in drinking water.
Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2010; 147(1):31-36.
[Show abstract][Hide abstract] ABSTRACT: A minimally invasive approach is described for sampling Fe, Cu, Zn and Mn in iron-gall ink. Filter paper (2 × 5mm) that is
moistened with de-ionized water is used to extract metals from an iron-gall ink surface. The extraction requires about 30–120s
for a small quantity of ink to diffuse into the moistened filter paper. The metals in the ink are extracted from the filter
paper using 50µL of concentrated nitric acid in a 2mL polystyrene beaker for approximately 10min. Graphite furnace atomic
absorption spectrometry (GFAAS) was used to quantify Fe, Cu, Zn and Mn in iron-gall ink. In order to test the feasibility
of this extraction procedure, the ratio of Fe:Cu was determined from ink lines that were drawn with a commercially available
iron-gall ink on modern acid-free paper. The measured ratio of Fe:Cu was 18.2:1 which is comparable to the expected ratio
of 20:1. The slightly lower ratio achieved using the extraction procedure and GFAAS was possibly due to the higher solubility
of the Cu species in the ink. One of the advantages of using a moistened filter paper is that only the ink surface is sampled
which avoids the possible measurement of metals of different inks of other components that may be present in the paper or
on the opposite side of the paper.
KeywordsIron-gall ink-Atomic spectroscopy-X-ray fluorescence (XRF)-Graphite furnace atomic absorption spectrometry (GFAAS)
[Show abstract][Hide abstract] ABSTRACT: In this paper, partitioning behaviors of typical neutral (Alanine), acidic (Glutamic acid) and basic (Lysine) amino acids into imidazolium-based ionic liquids [C(4)mim][PF(6)], [C(6)mim][PF(6)], [C(8)mim][PF(6)], [C(6)mim][BF(4)] and [C(8)mim][BF(4)] as extracting solvents were examined. [C(6)mim][BF(4)] showed the best efficiency for partitioning of amino acids. The partition coefficients of amino acids in ionic liquids were found to depend strongly on pH of the aqueous solution, amino acid and ionic liquid chemical structures. Different chemical forms of amino acids in aqueous solutions were pH dependent, so the pH value of the aqueous phase was a determining factor for extraction of amino acids into ionic liquid phase. Both water content of ionic liquids and charge densities of their anionic and cationic parts were important factors for partitioning of cationic and anionic forms of amino acids into ionic liquid phase. Extracted amino acids were back extracted into phosphate buffer solutions adjusted on appropriate pH values. The results showed that ionic liquids could be used as suitable modifiers on the stationary phase of an HPLC column for efficient separation of acidic, basic, and neutral amino acids.
[Show abstract][Hide abstract] ABSTRACT: This paper demonstrates a novel implementation of a net analyte signal (NAS) algorithm for resolving kinetic model. The evaluation of spectroscopic kinetics data by the established hard-modeling approach assumes that all the variation related to the response is linked to the species involved in the kinetic process. If effects are present in the data that cannot be explained by the model, such as baseline drift or inert interference, the estimated rate constant might be incorrect. An iterative net analyte signal procedure is shown to yield good rate constant estimates when the spectroscopic data is influenced by additional sources of variance. Simulated and real examples are used to confirm this statement.
Chemometrics and Intelligent Laboratory Systems 08/2009; 98(1):78-87. · 2.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work the catalytic role of unsupported gold nanoparticles on the luminol-hydrazine reaction is investigated. Gold nanoparticles catalyze the reaction of hydrazine and dissolved oxygen to generate hydrogen peroxide and also catalyze the oxidation of luminol by the produced hydrogen peroxide. The result is an intense chemiluminescence (CL) due to the excited 3-aminophthalate anion. In the absence of gold nanoparticles no detectable CL was observed by the reaction of luminol and hydrazine unless an external oxidant is present in the system. The size effect of gold nanoparticles on the CL intensity was investigated. The most intensive CL signals were obtained with 15-nm gold nanoparticles. UV-vis spectra and transmission electron microscopy studies were used to investigate the CL mechanism. The luminol and hydroxide ion concentration, gold nanoparticles size and flow rate were optimized. The proposed method was successfully applied to the determination of hydrazine in boiler feed water samples. Between 0.1 and 30 microM of hydrazine could be determined with a detection limit of 30 nM.