فهرست مطالب

Analytical & Bioanalytical Electrochemistry
Volume:5 Issue: 5, Oct 2013

  • تاریخ انتشار: 1392/10/10
  • تعداد عناوین: 10
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  • Khiena Z. Brainina, Elena L. Gerasimova, Daria P. Varzakova, Yan E. Kazakov, Leonid G. Galperin Pages 528-542
    Free radical oxidation ensures regular metabolism in human body. In case of oxidant/antioxidant misbalance free radical oxidation may lead to oxidation of lipids,membrane destruction and irreversible changes in DNA. Many diseases are both causes and consequences of oxidative stress. Its monitoring is essential for selecting and using modern therapy, thus reducing and preventing oxidative stress and irreversible changes in human body. The article describes a new electrochemical method of determining antioxidant/oxidant activity (AОА/ОА) of skin. The source of information is the platinum electrode potential shift observed when the investigated part of skin came into contact with a medium containing mediator system. An ECG-type electrode served as a reference one.To prove the reliability of the data obtained with the proposed method, model systems, containing antioxidants or oxidants in different concentrations were investigated. The data obtained showed high selfdescriptiveness and reliability of the results. The data demonstrating the impact of cosmetic creams on skin AOA are presented. The interrelation between skin AOA/OA and the presence of cardiovascular pathologies is proved.
    Keywords: Potentiometry, Oxidant Activity, Antioxidant Activity, Skin, Noninvasive, Cosmetics, Cardiovascular Pathologies
  • Hadi Beitollahi, Mohammad Ali Taher, Malihe Ahmadipour, Rahman Hosseinzadeh Pages 543-554
    Electrocatalytic oxidation of cysteamine at a carbon paste electrode modified with benzoylferrocene has been studied. The modified electrode showed excellent electrocatalytic activity toward cysteamine oxidation in phosphate buffer solution (PBS) (pH 7.0) with an overpotential of about 225 mV lower than that of the bare electrode. Under the optimized experimental conditions, the proposed electrochemical cysteamine sensor exhibited a linear calibration plot ranged from 7.0×10−8 to 2.5×10−4 M with a detection limit of 5.0×10−8 M. Also, Square wave voltammetry (SWV) was used for simultaneous determination of cysteamine and folic acid at the modified electrode. Finally, the proposed method was applied to the determination of cysteamine and folic acid in urine.
    Keywords: Cysteamine, Folic Acid, Voltammetry, Carbon Nanotube Paste Electrodes
  • S. Sharath Shankar, Bahaddurghatta E. Kumara Swamy, Kurangalara R. Mahanthesha, Chandrashekar C. Vishwanatha, Mohan Kumar Pages 555-573
    A cationic surfactant tetradecyl trimethyl ammonium bromide modified carbon pasteelectrode (TTABMCPE) was fabricated and the electrochemical behavior of norepinephrine at the modified electrode was investigated by cyclic voltammetric and differential pulse voltammetric techniques. A well-defined oxidation peak was observed at 174 mV and the significant increase in peak current at modified carbon paste electrode compared to bare carbon paste electrode was obtained. The effect of scan rate on the oxidation of norepinephrine was examined and it was found that the anodic peak current was proportional to the concentration of norepinephrine in the range from 0.10 μM to 4 μM. Comparedwith other reported electrochemical method; this new sensingmethod has higher sensitivity, rapid response and extreme simplicity. TTABMCPE was used for the simultaneous determination of nor norepinephrine, ascorbic acid and uric acid.The analytical performance of this biosensor has been evaluated for the detection of norepinephrine in injection sample.
    Keywords: Surfactant, Norepinephrine, Tetradecyl trimethyl ammonium bromide, Cyclic voltammetry, Differential pulse voltammetry
  • Marwa S. Elazazy, Wafaa S. Hassan, Manal S. Elmasry Pages 574-587
    In this study, spectroscopic and conductometric investigations of the interactions between oxyphenonium bromide (OXBr) and two dyes; chromotrope 2R (C2R) and ammonium reineckate (AMRT) are reported. The solubility product constant as well as other parameters related to the process of precipitating OXBr is premeditated operating the conductometric procedure. Moreover, contemporary approaches towards equivalence point localization have been pursued and compared. In this itinerary, the numerical differential conductivity methods were objective and systematic. However, Boltzmann sigmoid fitting model was more adequate for data analysis with less errors compared to the conventional and the differential methods. A molar ratio of (1:1) (OXBr:reagent) complexes in aqueous solutions have been determined conductometrically.The described procedures allowed the investigation of OXBr within the range of 3-15 mg using both reagents. Moreover, the obtained precipitate has been spectroscopically characterized using IR and 1H-NMR. The proposed conductometric method was applied successively to pharmaceutical formulations containing OXBr and the results obtained were favorably compared with those obtained using the reference method.
    Keywords: Conductometry, Spectroscopy, Oxyphenonium bromide, Pharmaceuticals, Solubility product constant, Differential conductivity, Boltzmann sigmoid
  • Dharampal Singh Tyagi, Aishwarya Singh Pages 588-596
    1,1’-[benzene-1,4-diyldimethylylidene]bis(3-phenylurea)) was synthesized and tested for the fabrication of aluminum selective membrane electrode. The membrane electrode with dimethyl phthalate (DMP) as plasticizer works satisfactorily in the linear concentration range of 1.3×10-6 to 1.0×10-1 M with best optimized composition of DMP: PVC: ionophore: NaTPB of 60:35:3:2 (%, w/w). The membrane electrode has a fast response time (5 s) and wide pH range (2.5–8.5). The selectivity coefficients were calculated with fixed interference method. The membrane sensor was also used as an indicator electrode for the titration of Al(III) with EDTA and Na3PO4.
    Keywords: Aluminum, Ion, selective electrode, Ionophore, Selectivity
  • Eskandar Omidinia, Ali Khanehzar, Nasrin Shadjou, Hamid Shahbazmohamadi, Shahriar Hojati Emami, Mohammad Hasanzadeh Pages 597-608
    A new strategy was developed to investigate conducting polymer poly(3,4-ethylenedioxy)thiophene:poly(styrenesulfonate) (PEDOT:PSS) properties and potential for enzymatic electrochemical detection of l-phenylalanine. PEDOT:PSS was blended with polyvinyl alcohol (PVA) and further treated with glutaraldehyde (GA) to produce new conducting polymer composite films of PEDOT:PSS/PVA-GA on indium(tin) oxide (ITO)-coated glass slides. Phenylalanine dehydrogenase (PheDH) was covalently immobilized on the glutaraldehyde modified conducting polymer composite films to produce PEDOT:PSS/PVA-GA-PheDH films. Using this strategy, PEDOT:PSS remained chemically unmodified and its electrical properties was maintained in a matrix containing glutaraldehyde modified polyvinyl alcohol. Electrochemical behavior of the conducting polymer composite films, before and after enzyme immobilization, was investigated using a potentiostat/galvanostat. Cyclic voltammograms showed an oxidation peak of about 0.63 V for PEDOT:PSS/PVA-GA (PEDOT:PSS to PVA ratio=1/1) and about 0.73 V forPEDOT:PSS/PVA-GA-PheDH in different concentrations of L-phenylalanine in Glycine/KCl/KOH buffer solution (100 mM, pH=10.4). The redox properties of PEDOT:PSS/PVA-GA films which is attributed to oxidation of PEDOT seems to contribute to electron transfer to the electrode during enzymatic reaction. Results showed that the system is suitable for determination of L-Phe in human urine for people with phenylketonuria.
    Keywords: Conducting Polymer, Poly(3, 4, ethylenedioxy)thiophene: poly (styrenesulfonate), Glutaraldehyde, Immobilization Matrix, Biosensing application
  • Ramesh S. Bhat, A. Chitharanjanhegde Pages 609-621
    Acidic sulphate bath having ZnSO4.7H2O, CoSO4.7H2O, NiSO4.7H2O and thiamine hydrochloride (THC) and citric acid (CA) in combination, was optimized for deposition of bright Zn-Co-Ni alloy coating on mild steel. Bath constituents and operating parameters were optimized by Hull cell method, for highest performance of the coating against corrosion. The effect of current density (c.d.), on deposit characters, such as corrosionresistance and hardness, thickness were studied and discussed. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion behaviors. The composition of deposits were determined by spectrophotometeric method and confirmed by EDX analysis. Surface morphology of the deposits was examined using scanning electron microscopy (SEM). The Zn-Co-Ni alloy, with intense peaks corresponding to Zn (100) and Zn (101) and Zn (110) phases, showed highest corrosion resistance, evidenced by X-ray diffraction (XRD) study. A new and cheap sulphate bath, for bright Zn-Co-Ni alloy coating on mild steel has been proposed, and results are discussed.
    Keywords: Electrodeposition, Phase structure, Surface Morphology, Corrosion Resistance, Ternary Zn–Co, Ni alloy
  • Safa A. M. Riad, Nouruddin W. Ali Pages 622-634
    Three novel techniques for selective determination of Cilostazol in presence of its oxidative degradation product were described. The three techniques involve the construction and studying of electrochemical response characteristics of novel poly (vinyl chloride) [PVC] matrix membrane sensors for cilostazolcation by using the ion-association complexes of this cation with sodium tetraphenyl borate (NaTPB), phosphotungestic acid (PTA) and ammonium reineckate (amm.RNC) counter anions as ion exchange sites in a plasticized PVC matrix, either as ion selective membranes, microcoated wire or as micro sized graphite selective sensors. The preparation and full characterization of these sensors, including composition, life span, usable pH range, response time and temperature were described. The electrodes were used for potentiometric determination of cilostazol in pure form, pharmaceutical products, plasma and in presence of its oxidative degradation product. These sensors showed near-Nernstian slopes of 56.14, 58.82, 56.23, 56.7, 59.14, 56.84, 58.72, 59.44 and 58.37mV over the concentration ranges of 1.0×10-7-1.0×10-2 M for NaTPB and PTA sensors and 1.0×10-6-1.0×10-2 M for amm.RNC sensors. The electrodes show good selectivity for cilostazol relative to a large number of inorganic cations, organic cations, sugars and amino acids. The behavior of the three sensors in presence of human plasma was also studied and reasonable results were obtained. The methods were successfully applied for determination of the intact drug in bulk powder and in presence of its oxidative degradation product; therefore it can be used as stability indicating methods.
    Keywords: Cilostazol, Sodium tetraphenyl borate (NaTPB), Phosphotungestic Acid (PTA), Ammonium reineckate (amm.RNC), PVC sensors, Plasma
  • Neelamyugandhar Sreedhar, Marella Sunil Kumar Pages 635-646
    A highly sensitive voltammetric method was developed for the determination of parathion in biological samples using sulphonatedpolyaniline modified glassy carbon electrode. The modified electrode was electrochemically fabricated by cyclic voltammetric method. Electrochemical reduction of parathion at modified electrode was investigated by cyclic voltammetry and differential pulse voltammetry. The instrumental parameters and reaction conditions were optimized for the development of stripping voltammetric procedure for the determination of parathion. A linear relationship was found between the peak current due to the reduction of nitro group to hydroxylamine and parathion concentration over the range from 1.0×10-8 to 2.0×10-5 M with detection limits of 1.5×10-9 M. The applicability of the proposed method was demonstrated by the determination of parathion in spiked human urine samples.
    Keywords: Parathion, Sulphonated polyaniline, Glassy carbon electrode, Voltammetry, Human urine samples
  • Alisa Kozitsina, Ekaterina Pomorceva, Yulia Suntsova, Jakov Beykin, Yulia Lagereva, Ludmila Tulakina, Anatoly Matern, Khiena Brainina Pages 647-664
    An increasing use of nanomaterials requires careful assessment of their toxicity, ways of biological interactions, and possible consequences for living organisms. A variety of nanomaterials and fragmented studies of nanomaterial toxic effects on living organisms have led to contradictory views on their safety. The article proposes a potentiometric method of evaluating antioxidant activity of biological systems, which gives an indication of oxidative stress. Cell lines WI-38 and L20B, introduced with gold and silver nanoparticles, were used as samples. The work demonstrates a correlation between cell viability, cytokine status, the level of antioxidant activity and concentrations of Ag and Au nanoparticles, absorbed by cells. Determination of the quantity of nanoparticles absorbed by cells and antioxidant concentration in cells can serve as optional methods of assessing a negative impact of nanoparticles on living substrates.
    Keywords: Potentiometric method, Oxidative stress, Antioxidant activity, Electron microscopy studies, Cell culture, Nanoparticles of noble metals, Stripping voltammetry