فهرست مطالب

Analytical & Bioanalytical Electrochemistry
Volume:5 Issue: 2, Apr 2013

  • تاریخ انتشار: 1392/03/25
  • تعداد عناوین: 10
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  • Pamula Raghu, Matti Mohan Reddy, Tukiakula Madhusudana Reddy *, Bahaddurghatta E. Kumara Swamy, Kasetty Reddaiah Pages 139-153

    Acetylcholinesterase (AChE) enzyme was immobilized through the silica sol–gel process onto the surface of carbon paste electrode (CPE). This fabricated monoenzyme biosensor on CPE was used as a working electrode. The enzyme biosensor on reaction with acetylthiocholine chloride (ASChCl or substrate), was found to be enzymatically hydrolyzed to thiocholine and acetic acid, which intern gave a disulfide compound and produced a larger anodic current at 0.63 V. The AChE biosensor was used for determining the two organophosphorous pesticides i.e. quinalphos and malathion in 0.1 M phosphate buffer 0.1 M KCl. The effect of scan rate, pH, enzyme loading and substrate concentration on the biosensor response was studied. Calibration graphs were performed for a concentration range of 20–300 ppb and 0.07–1.3 ppm for quinalphos and malathion respectively by employing the fabricated biosensor electrode. The limit of detection and limit of quantification values was found to be 8 ppb, 0.058 ppm and 26 ppb, 0.194 ppm for quinalphos and malathion respectively.

    Keywords: Biosensor, Acetylcholinesterase, Acetylthiocholine Chloride, Sol–Gel Immobilization, Quinalphos, Malathion
  • Fei Xiao, Lifeng Yang, Faqiong Zhao, Baizhao Zeng Pages 154-165
    Mercapto-imidazolium ionic liquid (IL, i.e. 1-methyl-3(2’-mercaptoacetoxyethyl) imidazolium hexafluophosphate)–graphite composite film is prepared. AuNi nanoparticles are electrodeposited on it from aqueous electrolyte. The resulting composite film coated glassy carbon electrode (AuNi–IL–graphite/GCE) is characterized by scanning electron microscopy, energy dispersive X–ray spectroscopy, X–ray diffraction and electrochemical impedance spectroscopy. The electrochemical redox of hydroquinone on the composite film is investigated. The results show that the AuNi–IL–graphite has high catalysis and stability. In neutral solutions, it can yield sensitive and stable amperometric response to hydroquinone. At 0.05 V (vs. SCE) the response current is linear to hydroquinone concentration in the range of 0.5–40 μM, with a detection limit of 0.05 μM (S/N=3) and sensitivity of 0.92 mA cm 2 μM-1.
    Keywords: AuNi Alloy Nanoparticles, Graphite, Electrodeposition, Ionic Liquid, Hydroquinone
  • Eman S. Elzanfaly*, Marianne Nebsen Pages 166-177
    This paper presents a comparative study between four sensors constructed to determine benoxinate hydrochloride (BX) in the presence of its hydrolysis induced degradation product using different ion association complexes and plasticizers. Precipitation based technique was used for sensors fabrication. The BX complexes with the cationic exchangers; BX- reinikate, BX-tetraphenylborate, BX-phosphotungestate, and BXtetrakis were obtained in situ by soaking the PVC membranes in 1×10-2 BX solution. Dioctylphthalate and nitrophenyl octyl ether were used as solvent mediators. The proposed sensors showed fast, stable Nernstian responses across a relatively wide BX concentration range (5×10-5 to 10-1 M) in the pH range of 4-6. The suggested sensors could be used for several weeks without any measurable change in sensitivity. They displayed good selectivity for BX in presence of its degradation product, common inorganic and organic species. The proposed sensors were successfully applied for the determination of BX in pure powder form and eye drops where good recoveries were obtained.
    Keywords: Benoxinate Hydrochloride, Stability Indicating Method, Reinikate, Tetraphenylborate, Phosphotungestate, Tetrakis
  • Sohrab Ershad*, Khdijeh Dideban, Farzaneh Faraji Pages 178-192
    A composite of polyaniline with multi-wall-carbon nanotubes (PANi/MWCNTs) was synthesized by an in situ chemical oxidative polymerization method. The PANi were synthesized chemically using aniline as the monomer and ammonium peroxydisulfate as the oxidant. The PANi/MWCNTs were characterized physically using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). With this nano composite as the modifier, a voltammetric sensor for folic acid (FA) was constructed on a glassy carbon electrode (GCE). Folic acid undergoes a 2e-/2H+ transfer electrochemical reduction process at 0.7 V with respect to Ag/AgCl reference electrode in pH 7. PANi/MWCNTs modified electrode showed good cyclic voltammetric (CV) response in wide linear range from 10-6 M to 10-4 M. This modified showed excellent sensitivity and stability for determination of folic acid. The response mechanism of folic acid at PANi-MWCNTs/GCE was discussed in detail.
  • Chinnappan Jayakumar, Vedhakkani Jeseentharani, Yerramala Subba Reddy, Manickam Anbu Kulandainathan, Karachalacheruvu Seetharamaiah Nagaraj, Boniface Jeyaraj* Pages 193-205
    A new modified glassy carbon electrode (GCE) was prepared using gold nanoparticles functionalized by 8-HQ. This modified surface was characterized by cyclic voltammetry, differential pulse voltammetry, scanning electron microscopy and FT-Raman spectroscopy. The modified electrode exhibits strong electrocatalytic activity towards the oxidation of a mixture of L-dopa and ascorbic acid (AA) with reduction of over potentials. Simultaneous analysis of this mixture at the conventional bare electrode surface is not feasible. However, two well-resolved oxidation peaks for AA and L-dopa are observed in the modified electrode and can be used for the estimation of AA and L-dopa simultaneously. Simultaneous analysis of AA and L-dopa using the DPV method, shows that the oxidation current is linear with L-dopa concentration in the range of 3.0–10 μM with a detection limit of about 0.31 μM (S/N=3). The proposed method was applied for the detection of L dopa in real samples.
    Keywords: 8, hydroxyquinoline, Gold Nanoparticle, L, dopa, Ascorbic Acid, Modified Electrode
  • Tanvir Arfin*, Rani Bushra, Roelof J. Kriek Pages 206-221
    In continuation to our previous work with composite polyaniline-zirconium (IV)- arsenate (PZA), we further extended with the conductivity measurements in this report. All the calculations reported in here were extracted from the experiments carried out in the temperature range of (25-50)±0.1°C and at different concentrations (0.01C(M)1) of KCl, NaCl and LiCl 1-1 electrolyte solutions. The diffusion coefficient for 1-1 electrolyte solutions was found to decrease in the order K+> Na+> Li+, which is in accordance with a decrease in the size of cation. The resistance is decreasing with increasing time in the order Li+> Na+> K+, and is due to an increased size of the cation for the chosen electrolytes. From the results, the conductivity values for 1-1 electrolytes in the membrane phase were found to be higher at the lower concentration for all the electrolytes in the order of Li+> Na+> K+. It was observed that the conductivity found to be increased with an increase of temperature and obeyed the Arrhenius equation. The activation energy increased with an increased concentration of electrolyte solution and the sequence for the energy of activation is Li+> Na+> K+. The Gibbs free energy, enthalpy and entropy for the ions were calculated at different concentrations and temperatures. All the values of G, H, and S were found to be positive in nature and are following the order K+> Na+> Li+.
    Keywords: Ionic Conductivity, Alkali Halides, Composite Polyaniline Zirconium (IV) Arsenate Membrane, Gibbs Free Energy, Membrane Conductivity, Diffusion Coefficient, Activation Energy
  • Fatma M. Abdel, Gawad*, Ahmed G. Helmy, Eman F. Mohamed Pages 222-235
    A simple and accurate potentiometric titration method for the determination of lamivudine and dothiepin hydrochloride is developed. For this purpose, two N bromoimides, viz., N-bromosuccinimide (NBS) and N-bromophthalimide (NBP) were used as titrants for determination of the two drugs in acid medium and the end point is determined using a platinum indicator electrode. The method was successfully applied for the determination of two drugs in their pure state or pharmaceutical preparations with mean recovery values of 99.67-100.10 and 99.55-100.33% and relative standard deviations (RSD) were 0.16-0.38 and 0.29-0.58% for lamivudine and dothiepin hydrochloride, respectively. Statistical comparison of the results with official and reported methods showed excellent agreement.
    Keywords: Lamivudine, Dothiepin Hydrochloride, N, Bromosuccinimide, N, Bromophthalimide, Potentiometric Titration
  • Hind Hammouch*, Ahmed Dermaj, Driss Chebabe, Pascal Decaro, Najat Hajjaji, Naima Bettach, Hisasi Takenouti, Abdellah Srhiri Pages 236-254
    The aim of this work is to characterise seed oil of opuntia ficus indica and to develop a new formulation to inhibit carbon steel corrosion in acidic medium. “OTH”, is a new environmentally friendly corrosion inhibitor containing Opuntia ficus indica seed oil. Fatty acid composition was analysed by Gas-chromatography after transesterification to Fatty Methyl esters (FAMES). The Electrochemical Impedance Spectroscopy (EIS) and voltamperometry measurements were carried out for different concentrations and immersion times. Surface analyses were carried out by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The results obtained show that the main fatty acids of prickly pear seed oil were C16:0, C18:0, C18:1, C18:2. The content of unsaturated fatty acids was high (83%). Electrochemical measurements show that OTH acts as a good mixed corrosion inhibitor. This inhibitor formulation forms a thick film that plays a barrier layer on the iron surface to minimize the contact area with corrosive solution and hinder metal oxidation.
    Keywords: Opuntia Ficus Indica, Corrosion Inhibition, Carbon Steel, EIS
  • Akbar Islamnezhad*, Jamshid Mofidi, Hamed Madahi, Kamal Mohammadi Pages 255-264
    The electrochemical behavior of Galantamine (Gal) in aqueous media has been examined by cyclic and differential pulse voltammetry. The voltammograms were recorded with μA utolab FRA2 Potentiostat-Galvanostat. A three-electrode system was used with a glassy carbon as working electrode, a platinum rod as the counter electrode and an Ag/AgCl as the reference electrode. All tests were carried out under room temperature and N2 atmosphere. The pH strongly affects the peak potential of Gal. The best analytical response was obtained at pH 2.0. The cathodic peak currents were proportional to Gal concentrations in the range of 0.1–10 mM under the optimized experimental conditions. The detection limit was 0.02 mM. The effect of potential scan rate on the peak potential and peak current of Gal was investigated. The correlation of the peak currents against v1/2 (v is the scan rate) is linear, which is very similar to a diffusioncontrolled process. Proposed method applied to analysis of commercial tablets, successfully.
    Keywords: Galantamine, Differential Pulse Voltammetry, Glassy Carbon Electrode
  • K. S. Beenakumari* Pages 265-269
    Nano sized nickel titanate particles were synthesized by using electrochemicalmethods. The nickel titanate particles produced are characterized by XRD, TG, UV-Visabsorption and FTIR analysis. Electrochemical method is found suitable for producing nickeltitanate particles. The particle size was calculated based on the Scherer equation and theaverage particle size was found to be 50 nm.
    Keywords: Nickel titanate, Electrochemical Method, Band Gap, Photocatalyst