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Ardabil, Iran

An electronic nose (EN) based on an array of chemiresistors, combined with a preconcentrator unit, for the detection of some volatile organic vapors was developed. In order to choose the proper polymers, seven potential polymers were chosen from numerous available polymers according to the principle of the linear solvation energy relationship (LSER). Different possible sensors arrays (128 arrays) composed of these seven polymers were designed by full factorial design (FFD). Principal component analysis (PCA) showed that four of seven polymers had enough ability to recognize different gas classes. By using Hierarchical cluster analysis (HCA), the tested polymers were categorized into four main groups with respect to their recognition ability. Combination of the FFD with PCA and HCA, brought to the identification of 8 proper arrays containing four polymers in each array. Precisely evaluation of predicted arrays with respect to their calculated resolution factors showed that the electronic nose containing the polymers of 75% pheny125% methylpolysiloxane (OV25), hexafluoro-2-propanolsubstituted polysiloxane (SXFA), poly bis(cyanopropyl)-siloxane (SXCN) and poly(ethylene maleate) (PEM) was the most proper design for recognition of analytes of interest. The fabricated EN was used successively for target gas recognition at three different concentrations. © 2009 Elsevier B.V. All rights reserved. Source

A new molecularly imprinted polymer material having urea molecule selective cavities was introduced. Urea was properly dissolved in acetonitrile in the presence of an acidic functional monomer. Molecularly imprinted polymers with different compositions were examined and the roper formulation was selected. It was shown that the MIP had a considerable selectivity for urea in comparison to similar compounds such as thiourea and hydroxyurea. The obtained polymer was used as an adsorber for solid phase extraction (SPE) of urea in the aqueous samples. The extracted urea was determined by using a spectrophotometric method. Different parameters of SPE were optimized and the developed procedure was used for urea determination in real samples. The calibration graph of the method was linear in the range of 0.6-8.3μmolL-1. The detection limit was calculated to be 0.14μmolL-1. © 2010 Elsevier B.V. Source

Alizadeh T.,University of Mohaghegh
Separation and Purification Technology | Year: 2013

A new chromatographic procedure was developed for the separation of atenolol (ATN) enantiomers based upon chiral ligand-exchange principal. The separation was carried out on a C8 column. l-alanine and Cu 2+ were applied as chiral selector and central bivalent complexing ion, respectively. It was found that the kind of copper salt had vital effect on the enantioseparation. The separation on the C8 stationary phase was more efficient than that on the C18 column. The pH of mobile phase, organic modifier content of mobile phase, mole ratio of chiral ligand to bivalent ion and Cu(l-alanine)2 concentration in the mobile phase were found to be important in enantiomers resolution efficiency. Water/methanol (70:30) mixture containing l-alanine-Cu2+ (2:1) was found to be the best mobile phase condition for ATN enantioseparation. The concentration of Cu(l-alanine)2 complex in the mobile phase influenced either enantiomers resolution efficiency or the detection sensitivity. All effective parameters were optimized in order to satisfy both detection sensitivity of the method and its separation efficiency. The optimized HPLC method was utilized in some synthetic and human blood plasma samples. © 2013 Elsevier B.V. All rights reserved. Source

The aim of the present study is to investigate the problem of modulation instability of an intense laser beam in the hot magnetized electron-positron plasma. Propagation of the intense circularly polarized laser beam along the external magnetic field is studied using a relativistic fluid model. A nonlinear equation describing the interaction of the laser pulse with the magnetized hot pair plasma is derived based on the quasi-neutral approximation, which is valid for the hot plasma. Also, the nonlinear dispersion equation for the hot plasma is obtained. The growth rate of the instability is calculated and its dependence on temperature and external magnetic field are considered. © 2012 American Institute of Physics. Source

In this work, recognition of target molecules by nano- and micro-sized molecularly imprinted polymers (nano-MIP and micro-MIP) was investigated by using electrochemical impedance spectroscopy (ESI). Modification of carbon paste electrode (CP) with promethazine (PMZ)-imprinted and non-imprinted polymers (MIP and NIP) influenced its ESI behavior, in both low and high frequency regions, approximately in the same manner. However, adsorption of target molecules on the electrodes, modified with different polymeric materials, influenced dissimilarly their ESI behaviors. Target molecules adsorption decreased bulk resistance of the MIP-based electrodes, whereas sorption of cross-reactant molecule increased this parameter of the electrode. This effect for bulky MIP-based electrode was more than that for the nano-MIP electrode. Swelling of the MIP materials, after target molecule recognition, was proposed as a main proof for this observation. However, bulk resistance of the NIP-based electrodes increased with adsorption of both target and foreign molecule. Swelling experiment indicated that in the presence of an organic solvent the bulky MIP particles expanded more than the nano-sized MIP. This led to erased memory effect in the bulky MIP. Scatchard plot showed that the recognition sites of the nano-sized MIP particles had more affinity to target molecule, compared to those of the bulky MIP particles. The prepared MIP based electrodes were used to plot the calibration curves based on the variation of bulk resistance of the electrodes versus PMZ concentration. Although, the MIP nanoparticles showed higher affinity for the target molecule the bulky MIP-based electrode was capable to determine target molecule at lower concentrations. © 2012 Elsevier B.V. All rights reserved. Source

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