• 전기화학회지
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• 제5권4호
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• pp.209-211
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• 2002

The simultaneous sensing of nitric oxide (NO) and its metabolite, nitrite $(NO_2^-)$ has been studied by Osteryoung square-wave voltarnmetery (OSWV) in physiological pH solution (0.1 M phosphate buffer solution, pH 7.2). Using an electrochemically pretreated glassy carbon (GC) electrode, OSWV was successfully applied to observe the well-separated oxidation peaks at ca. 0.58 and 0.80V vs. Ag/AgCI for NO and $(NO_2^-)$, respectively. This clear separation between the NO and $(NO_2^-)$ oxidation peaks may be due to the formation of surface oxides (e.g., quinone (C=O) or carboxylic $(COO^-)$ group) and surface defects introduced by the electrochemical pretreatment of GC electrodes.

• 전기화학회지
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• 제7권4호
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• pp.167-172
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• 2004

3,4-dihydroxybenzaldehyde(3,4-DHB) was oxidatively el electropolymerized on glassy carbon (GC) electrodes to prepare CC/p-3,4-DHB type electrodes, which were subsequently modified with 3,4-dihydroxybenzoic acid(3,4-DHBA) using 0.05M HCI as a catalyst. The esterification reactions were performed between -OH sites on the polymeric film surface of the p-3,4-DHB and the -COOH sites within the 3,4-DHBA molecules in solution. These reactions had a rate constant value of $1.1\times10^{-1}\;s^{-1}$ for the esterification step as obtained from the first-order rate constant in the solution. The electrochemical responses of the GC/p-3,4-DHB-3,4-DHBA electrodes exert an influence upon the buffer solution, its pH and applied potential ranges. The redox process of the electrode was more easily controlled by charge transfer kinetics than that of the CC/p-3,4-DHB. The modified electrodes had redox active sites that were 10 times more active than those present before modification. The electrical admittance of the modified electrodes was also three times higher than that of the unmodified electrodes. After being annealed in ethanol for 20 hrs the electrodes brought about a 3.3 times greater change of water molecules in the redox reaction. The modified electrodes are stable in the potential range of 0.4 to 0.55V.

• Bulletin of the Korean Chemical Society
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• 제29권9호
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• pp.1774-1780
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• 2008

New PVC based polymeric membrane electrodes (PME) and coated glassy carbon electrodes (CGCE) based on synthesized Schiff base complexes of Co(III); [Co(Salen)$(PBu_3)_2$]$ClO_4$, [Co($Me_2$Salen)$(PBu_3)_2$]$ClO_4$, [Co(Salen)$(PBu_3)H_2O$]$ClO_4$; as anion carriers for potentiometric determination of $ClO_4\;^-$were studied. The PME and also CGCE electrodes prepared with [Co(Me2Salen)$(PBu_3)_2$]$ClO_4$ showed excellent response characteristics to perchlorate ions. The electrodes exhibited Nernstian responses to $ClO_4\;^-$ ions over a wide concentration range with low detection limits ($1.0 {\times} 10^{-6}\;mol\;L^{-1}$ for PME and $9.0 {\times} 10^{-7}\;mol\;L^{-1}$ for CGCE). The electrodes possess fast response time, satisfactory reproducibility, appropriate lifetime and, most importantly, good selectivity toward $ClO_4\;^-$ relative to a variety of other common inorganic anions. The potentiometric response of the electrodes is independent of the pH in the pH range 2.5-8.5. The proposed sensors were used in potentiometric determination of perchlorate ions in mineral water and urine samples. The interaction of the ionophore with perchlorate ions was shown by UV/Vis spectroscopy.

• Bulletin of the Korean Chemical Society
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• 제33권6호
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• pp.1919-1924
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• 2012

Poly(anthranilic acid) was synthesized by rapid mixing method using 5-sulphosalicylic acid as a dopant. The synthesized polymer was characterized by various techniques like FT-IR, UV-Visible, and X-ray diffraction $etc.$, The FT-IR studies reveal that the 5-sulphosalicylic acid is well doped within the polymer. The morphological property was characterized by field emission scanning electron microscopic technique. The electrochemical properties of the polymer were studied by cyclic voltammetric method. The synthesized polymer was used to modify glassy carbon electrode (GCE) and the modified electrode was found to exhibit electrocatalytic activity for the oxidation of uric acid (UA).

• Archives of Pharmacal Research
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• 제24권4호
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• pp.355-359
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• 2001

A novel HPLC method with electrochemical detection has been developed for the determination of recombinant human epidermal growth factor (rhEGF) in pharmaceutical products. rhEGF was separated from other components in formulation on a reversed-phase C18 column with 24% acetonitrile in 0.1 M phosphate buffer (pH 4.75). The optimum electrochemical oxidation of EGF was obtained at 0.85 V vs. Ag/AgCl in a glassy carbon working electrode due to electroactive tyrosine, tryptophan, methionine, and arginine residues. The quantitation range was from 1.0 to 200 ng of rhEGF with the linear correlation coefficient greater than 0.999. The method was successfully applied for the quantitation of rhEGF in a pharmaceutical preparation.

• Bulletin of the Korean Chemical Society
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• 제18권8호
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• pp.850-856
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• 1997

A series of tetradentate Schiff-base ligands; 1,3-bis(salicylideneimino) propane, 1,4-bis(salicylideneimino)butane, and 1,5-bis(salicylideneimino)pentane, and their Cu(Ⅱ) and Ni(Ⅱ) complexes have been synthesized. The properties of ligands and complexes have been characterized by elemental analysis, IR, NMR, UV-Vis spectra, molar conductance, and thermogravimetric anaylsis. The mole ratio of Schiff base to metal at complexes was found to be 1 : 1. All complexes were four-coordinated configuration and non-ionic compound. The electrochemical redox processes of the ligands and their complexes in DMF solution containing 0.1 M TEAP as supporting electrolyte have been investigated by cyclic voltammetry, chronoamperometry, differential pulse voltammetry at glassy carbon electrode, and by controlled potential coulometry at platinum gauze electrode. The redox process of the ligands was highly irreversible, whereas redox process of Cu(Ⅱ) and Ni(Ⅱ) complexes was observed as one electron transfer process of quasi-reversible and diffusion-controlled reaction. Also the electrochemical redox potentials of complexes were affected by chelate ring size of ligands. The diffusion coefficients of Cu(Ⅱ) and Ni(Ⅱ) complexes in DMF solution were determined to be 4.2-6.6×10-6 cm2/sec. Also the exchange rate constants were determined to be 3.6-9.7×10-2 cm/sec.

• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.276-281
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• 2018

High concentration of copper in mezcal, a representative Mexican spirituous alcoholic beverage, is a serious problem due to the damage that it may cause to human health. A cyclic voltammetry and square wave anodic stripping voltammetry study of copper (II) in three commercial mezcal samples based on glassy carbon electrode response was undertaken. The analysis was developed using a simulated matrix solution ($EtOH/H_2O$ (1:1), 0.1 M $LiClO_4$ and AcOH/AcONa 0.05 M/0.008 M), with Cu (II) concentrations in the range 0 - 1 ppm. Direct electrochemical analysis of mezcal samples was complicated by the presence of different organic compounds in the matrix. The analytical signal of Cu (II) in the spirituous was notably improved and the interferences caused by organic compounds were minimized, by diluting the mezcal samples 10% with $EtOH/H_2O$ (1:1) solution. An efficient quantification of Cu (II) was obtained from the calibration curve by the SWASV and using the internal standard method (Cd (II)) in commercial samples (1.2-6.7 ppm); the results were correlated satisfactorily with the values obtained by AAS.

• Bulletin of the Korean Chemical Society
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• 제17권2호
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• pp.173-179
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• 1996

A series of tetradentate Schiff base ligands; [1,2-bis(naphthylideneimino)ethane, 1,3-bis(naphthylideneimino)propane, 1,4-bis(naphthylideneimino)butane, and 1,5-bis(naphthylideneimino)pentane] and their Ni(Ⅱ) complexes have been synthesized. The properties of these ligands and their Ni(Ⅱ) complexes have been characterized by elemental analysis, IR, NMR, UV-vis spectra, molar conductance, and thermogravimetric analysis. The mole ratio of Schiff base to Ni(Ⅱ) metal was found to be 1:1. The electrochemical redox process of the ligands and their Ni(Ⅱ) complexes in DMF and DMSO solution containing 0.1 M tetraethyl ammonium perchlorate (TEAP) as a supporting electrolyte have been investigated by cyclic voltammetry, chronoamperometry, differential pulse voltammetry, and controlled potential coulometry at glassy carbon electrode. The redox process of the ligands was highly irreversible, whereas redox process of Ni(Ⅱ) complexes were observed as one electron transfer process in quasi-reversible and diffusion-controlled reaction. The electrochemical redox potentials of the Ni(Ⅱ) complexes were affected by the chelate ring size of ligands. The diffusion coefficients of Ni(Ⅱ) complexes containing 0.1 M TEAP in DMSO solution were determined to be 5.7-6.9 × 10-6 cm2/sec. Also the exchange rate constants were determined to be 1.8-9.5 × 10-2 cm2/sec. These values were affected by the chelate ring size of ligands.

• Journal of Electrochemical Science and Technology
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• 제6권3호
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• pp.106-110
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• 2015

This study investigates Cu(II) complexes of cyclam, propylene cross-bridged cyclam (PCB-cyclam), and propylene cross-bridged cyclam diacetate (PCB-TE2A) as homogeneous electrocatalysts for CO₂ reduction in comparison with Ni(II)-cyclam. It is found that Cu(II)-cyclam can catalyze CO₂ reduction at the potential close to its thermodynamic value (0.75 V vs. Ag/AgCl) in tris-HCl buffer (pH 8.45) on a glassy carbon electrode. Cu(II)-cyclam, however, suffers from severe demetalation due to the insufficient stability of Cu(I)-cyclam. Cu(II)-PCB-cyclam and Cu(II)-PCB-TE2A are revealed to exhibit much less demetalation behavior, but poor CO₂ reduction activities as well. The inferior electrocatalytic ability of Cu(II)-PCB-cyclam is ascribed to its redox potential that is too high for CO₂ reduction, and that of Cu(II)-PCB-TE2A to the steric hindrance preventing facile contact with CO₂ molecules. This study suggests that in addition to the redox potential and chemical stability, the stereochemical aspect has to be considered in designing efficient electrocatalysts for CO₂ reduction.

• 한국재료학회지
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• 제21권3호
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• pp.180-185
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• 2011

This study is aimed to increase the activity of cathodic catalysts for PEMFCs(Polymer Electrolyte Membrane Fuel Cells). we investigated the temperature effect of 20wt% Pt/C catalysts at five different temperatures. The catalysts were synthesized by using chemical reduction method. Before adding the formaldehyde as reducing agent, process was undergone for 2 hours at the room temperature (RT), $40^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$, respectively. The performances of synthesize catalysts are compared. The electrochemical oxygen reduction reaction (ORR) was studied on 20wt% Pt/C catalysts by using a glassy carbon electrode through cyclic voltammetric curves (CV) in a 1M H2SO4 solution. The ORR specific activities of 20wt% Pt/C catalysts increased to give a relative ORR catalytic activity ordering of $80^{\circ}C$ > $100^{\circ}C$ > $60^{\circ}C$ > $40^{\circ}C$ > RT. Electrochemical active surface area (EAS) was calculated with cyclic voltammetry analysis. Prepared Pt/C (at $80^{\circ}C$, $100^{\circ}C$) catalysts has higher ESA than other catalysts. Physical characterization was made by using X-ray diffraction (XRD) and transmission electron microscope (TEM). The TEM images of the carbon supported platinum electrocatalysts ($80^{\circ}C$, $100^{\circ}C$) showed homogenous particle distribution with particle size of about 2~3.5 nm. We found that a higher reaction temperature resulted in more uniform particle distribution than lower reaction temperature and then the XRD results showed that the crystalline structure of the synthesized catalysts are seen FCC structure.