• Archives of Pharmacal Research
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• v.23 no.3
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• pp.197-201
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• 2000

In an aqueous piperacillin sodium solution, a well-defined single wave or single peak was observed by direct current(DC) polarography or differential pulse polarography(DPP). The peak potential change per pH unit was -54 mV in the phosphate buffer at $18^{\circ}C$, which indicated that protons were involved in the electrochemical reduction of the 2,3-dioxopiperazine moiety of piperacillin sodium with a $H^{+}e^{-}$ ratio of one. Using a phosphate buffer of pH 4.3, the $1.0{times}10^{-7}$ M piperacillin sodium single peak could be determined by DPP with relative standard deviation of 1.6 %(n=3). Piperacillin sodium could be analyzed with-out interference from penicillin G-potassium, which enabled the employment of DPP as a fast and simple technique for monitoring the synthetic process of the antibiotic.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.131-137
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• 2011

A simple and rapid electrochemical method for the quantitative analysis of $Mn^{2+}$ ion is demonstrated with a view to examine the $Mn^{2+}$ dissolution behavior of $LiMn_2O_4$. The method described herein is based on the oxidation reaction of $Mn^{2+}$ to $Mn^{4+}(MnO_2)$ in aqueous buffer solution. Under the optimum condition (pH 8.9 0.04 M $NH_3-NH_4Cl$ buffer solution and glassy carbon working electrode), the linear range of $5{\mu}M-100{\mu}M$ (0.275-5.5 ppm) [$Mn^{2+}$] is obtained for the Linear sweep voltammetry(LSV) and $0.2{\mu}M-10{\mu}M$ (0.011-0.55 ppm) [$Mn^{2+}$] for the differential pulse voltammetry (DPV), respectively. It is also noted that the oxidation reaction of $Mn^{2+}$ ion is reduced with increasing amount of the electrolyte ($LiPF_6$, EC, EMC) added to the measuring solution, which is found to be mainly due to $LiPF_6$ and EC rather than EMC.

• Bulletin of the Korean Chemical Society
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• v.23 no.3
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• pp.427-431
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• 2002

A screen printed graphite electrode has been developed for a simple and sensitive determination of phenolic compounds in an aqueous solution. The electrode developed uses a simple and effective screen printing technique with ${\alpha}-Cyclodextrin({\alpha}-CD)$ modified graphite ink. Phenols were captured on the surface of the ${\alpha}-CD$ modified electrode through complex formation. The phenol/ ${\alpha}-CD$ complex was deposited and quantified electrochemically using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The optimization of the experimental parameters was performed in regard to electrode composition, pH, temperature, sample preconcentration time. Interferences from other organic compounds were investigated. The detection limit for phenols was 500 ${\pm}7$ nM for DPV, with the linear range of 0.5 ${\mu}M$ -25.0 ${\mu}M$ and 30 ${\pm}2$ nM for SWV, with the linear range of 30 nM - $50{\mu}M$, respectively.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.415-419
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• 2012

Electrochemical characteristics of nitrite ion were investigated at a poly(methylene blue)-modified glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry. The poly(methylene blue)-modified glassy carbon electrode exhibited enhanced anodic signals for nitrite. The effects of key parameters on the detection of nitrite were evaluated at the modified electrode, such as pH, accumulation time, and scan rate. Under optimum condition, the chemically modified electrode can detect nitrite in the concentration range $2.0{\times}10^{-6}$ to $5.0{\times}10^{-4}$ M with the detection limit of $2.0{\times}10^{-6}$ M and a correlation coefficient of 0.999. The detection of nitrite using the chemically modified electrode was not affected by common ions such as $Na^+$, $K^+$, $Ca^{2+}$, $Cl^-$, $HPO_4^{2-}$ and $H_2PO_4^- $. The modified electrode showed good stability and reproducibility. The practical application of the present method was successfully applied to the determination of nitrite ion in cabbage samples.

• Journal of the Korean Electrochemical Society
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• v.19 no.4
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• pp.134-140
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• 2016

An aptamer-based biosensor using a new redox indicator has been examined for the electrochemical detection of thrombin. The aptamer modified primary aliphatic amine was covalently immobilized onto poly-(5,2':5',2"-terthiophene-3'-carboxylic acid) (polyTTCA) layer. Tetrabromophenolphthalein ethyl ester (KTBPE) was interacted to aptamer and used as an electrochemical indicator. Prior to the detection, the oxidation reaction of KTBPE onto aptamer modified layer was also investigated using differential pulse voltammetry. The characterization of the final sensor (KTBPE/aptamer -polyTTCA) was performed by voltammetry, QCM, and ESCA. After binding of thrombin onto KTBPE/aptamer based sensor, the peak signal of KTBPE was gradually decreased. The sensor exhibited a dynamic range between 10.0 and 100.0 nM with the detection limit of $1.0{\pm}0.2nM$.

• 한국전기화학회:학술대회논문집
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• 2000.10a
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• pp.7-7
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• 2000

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.138-144
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• 2010

In order to investigate the electrochemical propertied of titanium electrode for electrolysis, manganese oxide was electrodeposited on surface of mesh titanium by pulse voltammetry. The morphological changes and impedance results of manganese oxide electrodeposited electrode were analyzed by SEM and EDX. The size of electrodeposited manganese oxide on mesh titanium was increased with first cycle pulse time increase, and approximately 100 non-uniform manganese oxide was grown at 10 ms pulse polarization time. Charge transfer resistance($R_{ct}$) of near the overpotential was analyzed by EIS measurement and the feasibility of prepared electrode was evaluated by the overpotential calculated from Tafel plots.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1329-1334
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• 2006

The electrochemical reduction of coumarin, 7-acetoxy-4-methyl coumarin (AMC), and 7-acetoxy-4-bromomethyl coumarin (ABMC), in 0.1 M tetraethyl ammonium perchlorate/acetonitrile solution was carried out by direct current, differential pulse polarography, cyclic voltammetry, and controlled potential coulometry. The electrochemical reduction of ABMC was proceeded through three steps of electron transfer coupled with the chemical reactions. The color of solution was changed to yellow when the carbonyl group was reduced during 2nd step (-1.8 volts) and independented with cleavage of bromo group. Highest fluorescence intensity showed when the electrochemical reduction of AMC was controlled at near the potential (-2.3 volts vs. Ag/AgCl).

• Analytical Science and Technology
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• v.18 no.1
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• pp.89-95
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• 2005

Studies on the electrochemical reduction of 7-acetoxy-4-bromomethyl-coumarin (ABMC), 7-acetoxymethyl coumarin (AMC), and coumarin in 0.1 M tetraethyl ammonium perchlorate acetonitrile solution were carried out with direct current, differential pulse polarography, cyclic voltammetry, and controlled potential coulometry. The electrochemical reduction of ABMC was proceeded through three irreversible steps coupled with the chemical reactions. The solution color was changed to yellow when the carbonyl group was reduced during second step and the color change was independent with bromo group of ABMC. Fluorescent intensity was highest when the electrochemical reduction was controlled at near the overpotential of supporting electrolyte (-2.3 volts).

• Journal of the Korean Chemical Society
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• v.35 no.2
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• pp.165-171
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• 1991

The electrochemical reduction of carbon-6-dibromo groups on 6,6-dibromo penicillanic acid 1,1-oxide(DBPA) was investigated by direct current, differential pulse polarography, cyclic voltammetry and controlled potential coulometry. The irreversible two electrons transfer on the reductive debromination of each bromo group proceeded by EC,EC mechanism at the two electrode reduction steps(-0.48, -1.62 volts). The 6-bromo-PA and 6,6-dihydro-PA was synthesized by controlled potential electrolysis. Upon the basis of results on the products analysis and interpretation of polarograms obtained at various pH, electrochemical reaction mechanism was suggested.