فهرست مطالب

Analytical & Bioanalytical Electrochemistry
Volume:5 Issue: 3, Jun 2013

  • تاریخ انتشار: 1392/04/20
  • تعداد عناوین: 10
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  • Mohammad Hossein Maashhadizadeh, Reyhaneh Refahati, Ehsan Amereh Pages 270-282
    Ag/TiO2 nanocomposite was used as a modifier in carbon-paste electrode (CPE) to fabricate a carbamazepine (CBZ) voltammetric sensor. The results show an efficient catalytic activity of the electrooxidation of CBZ. Electrochemical behaviour of CBZ at the sensor was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Results showed that the modified electrode exhibited a strong electrocatalytic activity toward the redox of CBZ. The effects of scan rate and pH on peak current were investigated and an optimal scan rate of 50 mV s-1 and a pH 2.0, Britton-Robinson buffer solution (BR), were used. Under the optimum conditions, the catalytic peak currents of CBZ were linearly dependent on the concentrations of CBZ in the range from 2.5×10-6 to 1.0×10-4 mol L-1 with a detection limit of 8.6×10-7 mol L-1. This proposed method was successfully applied to determine the carbamazepin concentration in its tablet as real sample and a recovery of 95% was obtained without interference from tablet matrix.
    Keywords: Carbamazepin, Ag, TiO2 Nanocomposite, Modified Carbon Paste Electrode, Drug Samples, Differential Pulse Voltammetry
  • Lida Fotouhi, Shahrbanoo Arabiyan, Omran Moradlou Pages 283-290
    A film of multiwalled carbon nanotubes (MWCNT) was casted on the surface of an ionic liquid (IL) modified carbon paste electrode (CPE) to established a modified electrode denoted as MWCNT/IL/CPE. The electrochemical reduction of furazolidone (Fu) was investigated with cyclic voltammetry. The constructed electrode (MWCNT/IL/CPE) exhibited excellent electrocatalytic behavior toward the reduction of Fu as evidenced by the enhancement of the reduction peak current and the shift in the cathodic potential to less negative values (by 20 mV) in comparison with the bare CPE. The formal potential, E0', of Fu is pH dependent with a slope of -53.1 mV per unit of pH, close to the anticipated Nernestian value of -59 mV for a 4-electron and 4-proton process. A detailed analysis of cyclic voltammograms gave fundamental electrochemical parameters including the electroactive surface coverage (Г), the transfer coefficient () and the standard rate constant (ks). A linear calibration curve was obtained for Fu detection in the concentration range of 50-800 mol L-1 of detection limit 33 mol L-1.
    Keywords: Ionic Liquid, Cyclic Voltammetry, Multiwalled Carbon Nanotubes, Furazolidone, Modified Electrode
  • Pages 291-304
    An ECE mechanism in which chemical reaction is permanently in equilibrium is investigated theoretically. The calculations were performed by the method of numerical integration for fast and reversible electrode reactions as well as for the reactions that are controlled by the electron transfer kinetics. In square-wave voltammetry the response depends on the difference in standard potentials of individual electron transfers and on the dimensionless equilibrium constant of the chemical reaction. Depending on the concentration of compound X-, which is one of reactants in chemical reaction, either a single peak or the split response may appear. In the first case the peak potential depends linearly on the logarithm of X- concentration, with the slope -2.3RT/2F. The potential of the first peak of the split response is also linear function of, but the slope is -2.3RT/F. The relationship is determined between standard potentials and the critical value of the equilibrium constant above which the response splits in two peaks. Under the influence of electrode kinetics, the responses change with square-wave frequency. The first electron transfer is slow and the second one is fast if two peaks appear at the lowest frequency and merge into a single peak at the highest frequency. If the second charge transfer is slower that the first one, the difference in peak potentials increases with the increasing frequency.
    Keywords: Reversible ECE Mechanism, Square, wave Voltammetry, Theory, Kinetics of Electrode Reactions
  • Parisa Heidari, Shabnam Jalali, Zahra Mofidi, Abasali Zamani, Mohammad Reza Yaftian Pages 305-315
    Nitrobenzo18-crown-6 (NB18C6) has been examined as an ion sensing material for fabricating a PVC membrane lead ion-selective potentiometric sensor. The best performance of the electrode was observed with a membrane composition formed by 30% PVC, 58.5% ortho-nitrophenyloctylether (NPOE) as plasticizing solvent mediator, 9% of NB18C6 as ionophore and 2.5% sodium tetraphenylborate (NaTPB) as ion excluder. The electrode presents a nearly Nernstian response (a slope of 30.5±0.5 mV/decade) over a concentration range 1×10-5-1×10-2 M of lead ions, with a limit of detection 8.9×10-6 M. Its potential response was independent on the pH variation in the range 2.2-4.1. The dynamic response time of the electrode to achieve a steady potential was relatively fast and was found to be about 6 seconds. The selectivity of the prepared electrode relative to some mono-, di-, tri- and tetra-valent metal ions was examined. This electrode can be used for 3 months without considerable divergences in the potential response. It was successfully used as an indicator electrode for the complex formation titration of lead solutions by EDTA.
    Keywords: Lead, Nitrobenzo 18, Crown, 6, Ion Selective Electrode, PVC Membrane
  • Ali Ghaffarinejad, Einollah Magsoudi, Naghmeh Sadeghi Pages 316-324
    Platinum is a suitable electrode for electrochemical production of hydrogen, but it is expensive and its resource availability very limited. Shimalite Ni is a catalyst for reductionin gas chromatography, which commonly used for methane conversion of carbon monoxide, carbon dioxide, formaldehyde, and so on. In this study carbon paste electrode was modified by the proposed catalyst and the modified electrode was used for electrochemical hydrogen evolution in acidic media. Some parameters including oil and catalyst percentage in the paste, pH and supporting electrolyte type were examined. The best conditions and composition was 13% catalyst, 20% paraffin oil and 1.5 M H2SO4. Due to the low cost and high performance of this catalyst, it can be considered a good candidate for production of hydrogen without using Pt. Also against very reports, in this study by applying successive potential cycles on the modified electrode surface, the performance of the electrode improves.
    Keywords: Hydrogen Production, Shimalite Ni, Carbon Paste Electrode, Electrolysis
  • Mohamed Refaat Elghobashy, Osama Mohamed Badran, Maissa Yacoub Salem, Khadiga Mohamed Kelani Pages 325-340
    Azelastine Hydrochloride (AZT) was described by using the ion association complex between these drugs with either sodium tetraphenyl-borate (TPB) or ammonium reineckate (RNC) counter ions. The performance characteristics of the sensors were evaluated according to IUPAC recommendations, reveal a fast, stable and linear response over the concentration range 10-5- 10-2 M for AZT. The sensors are used for determination of AZT in eye drops and plasma. The developed method was found to be simple, accurate and precise when compared with the Manufacturer method.
    Keywords: Azelastine Hydrochloride, Ion Selective Electrode, PVC Membranes Ammonium Reineckate, Sodium Tetraphenyl, Borate
  • Chandrashekar C. Vishwanath, Bahaddurghatta E. Kumara Swamy, Tammanekar V. Sathisha, G. M. Madhu Pages 341-351
    Azelastine Hydrochloride (AZT) was described by using the ion association complex between these drugs with either sodium tetraphenyl-borate (TPB) or ammonium reineckate (RNC) counter ions. The performance characteristics of the sensors were evaluated according to IUPAC recommendations, reveal a fast, stable and linear response over the concentration range 10-5- 10-2 M for AZT. The sensors are used for determination of AZT in eye drops and plasma. The developed method was found to be simple, accurate and precise when compared with the Manufacturer method. Keywords- Azelastine Hydrochloride, Ion Selective Electrode, PVC Membranes Ammonium Reineckate, Sodium Tetraphenyl-Borate
  • Farhang Mizani, Maryam Moradi, Farnoush Faridbod Pages 352-367
    A new highly selective silver (I) electrode was prepared with a PVC membrane using 2-amino-N-(2-Mercapto phenyl) Benzamid (L) as an electroactive material, 2-nitrophenyloctylether (o-NPOE) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive in the percentage ratio of 3:5:57:35 (NaTPB:L:o-NPOE:PVC, w:w). Potentiometric evaluation of the poly(vinyl chloride) (PVC) membranes containing L showed excellent affinity and selectivity to silver (I) ion over alkali, alkaline earth and other transition metal cations. These electrode works well over wide range of concentration (1.0×10-2 to 1.0×10-7 M) with a Nernstian slope 59.1±0.2 mV/decade. The potentiometric responses are independent of the pH of the test solution in the pH range 2.9–10.3. The electrodes possess advantages of low resistance, fast response time and relatively long lifetimes. The electrodes were used, as indicator electrodes, in the potentiometric titration of silver ion and in the determination of Ag+ in waste water.
    Keywords: Silver Ion, Selective Electrode, PVC Membrane, 2, Amino, N, (2, Mercapto phenyl) Benzamid, Potentiometry, Sensors
  • Marianne Nebsen, Ghada Mostafa Elsayed, Mohammed Abdelkawy, Sona Zaki Elkhateeb Pages 368-380
    Three novel Xylometazoline Hydrochloride (XYLO) selective electrodes were investigated with Dioctyl phthalate (DOP) as a plasticizer in a polymeric matrix of polyvinyl chloride (PVC). Sensor 1 was fabricated using Phosphomolybdic acid (PMA) as an anionic exchanger without incorporation of an ionophore. Sensor 2 used 2-hydroxy propyl -cyclodextrin (hp-CD) as an ionophore while sensor 3 was constructed using calix[6]arene as an ionophore. Linear responses of XYLO within the concentration ranges of 10−4 to 10−2, 10−5 to 10−2 and 10−5 to 10−2 mol L−1 were obtained using sensors 1, 2 and 3, respectively. Nernstian slopes of 49.78, 56.21 and 46.20 mV/decade over the pH range of 5–9 for sensors 1, 2 and 5-7 for sensor 3 were observed. The selectivity coefficients of the developed sensors indicated excellent selectivity for XYLO. The utility of 2-hydroxy propyl -cyclodextrin and calix[6]arene as ionophores had a significant influence on increasing the membrane sensitivity and selectivity of sensors 2 and 3 compared to sensor 1. The proposed sensors displayed useful analytical characteristics for the determination of XYLO in bulk powder, different pharmaceutical formulations, and biological fluids (Rabbit aqueous humor) and in the presence of its degradation product (2, 6- dimethyl-4-tertbutyl- phenylacetic acid) and thus could be used as stability-indicating method.
    Keywords: Xylometazoline, Hydroxypropyl cyclodextrine, Calix[6]arene, Rabbit Aqueous Humor
  • Development of a Method for a Sensitive Simultaneous Determination of Acetaminophen and Tryptophan in Biological Samples
    Ali Babaei, Mojtaba Farshbaf, Mohammad Afrasiabi, Farzad Bamdad, Aliyeh Dehdashti Pages 381-394
    A chemically modified electrode is constructed based on multi-walled carbon nanotube modified glassy carbon electrode (MWCNTs/GCE) for simultaneous determination of acetaminophen (ACT) and tryptophan (TRY). The measurements were carried out byapplication of differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA) methods. Application of DPV method showed that the linear relationship between oxidation peak current and concentration of ACT and TRY were in the range of 2 μM to 360 μM, and 3 μM to 360 μM, respectively. Under optimal conditions the modified electrode exhibited high sensitivity and stability for both ACT and TRY determination, making it a suitable sensor for the simultaneous submicromolar detection of ACT and TRY in solutions. The analytical performance of modified electrode has been evaluated for detection of ACT and TRY in human serum and human urine with satisfactory results.
    Keywords: Acetaminophen, Tryotophan, Carbon Nanotube, Modified Glassy Carbon Electrode