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Amperometric Determination of Nitrite at Poly(Methylene Blue)-Modified Glassy Carbon Electrode
Xu, Guang-Ri,Xu, Guifang,Xu, Ming-Lu,Zhang, Zhengqing,Tian, Yuan,Choi, Han-Nim,Lee, Won-Yong Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.2
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.
Selective Determination of Quercetin Using Carbon Nanotube-Modified Electrodes
Xu, Guang-Ri,Kim, Sunghyun WILEY-VCH Verlag 2006 Electroanalysis Vol.18 No.18
<P>Electrochemical detection of quercetin has been carried out on glassy carbon electrodes modified with carbon nanotubes and Nafion (GC/Nafion-CNT). GC/Nafion-CNT electrodes did not show passivation effect that occurs on the unmodified electrodes and displayed better stability and reproducibility. Quercetin oxidation was most favorable in acidic conditions and current gradually decreased as the solution pH increased. No oxidation was observed when two &n.bond;OH groups in a catechol moiety were fully deprotonated. These electrodes enabled selective determination of quercetin in the presence of interfering species such as ascorbic acid, uric acid, glucose, and catechol in large excess. Quantification of quercetin in a yellow onion has been made and favorably compared with reported values. Good selectivity and high sensitivity obtained by Osteryoung sSquare-wave voltammetry can open new possibilities of direct quercetin determination in vegetables with a minimal sample treatment.</P>
Xu, Guang-Ri,Qi, Xin-hua,Yang, Fengxia,Lee, Jae-Joon,Xu, Ming-Lu,Zhang, Yu-Ping,Kim, Sunghyun WILEY-VCH Verlag 2009 Electroanalysis Vol.21 No.22
<P>A glassy carbon electrode having two polymer layers has been applied to selectively detect epinephrine. The inner layer formed by electropolymerization of macrocyclic nickel complex functioned as an electrocatalyst for epinephrine oxidation and the outer layer composed of hydrolyzed polyurethane γ-benzyl L-glutamate as a screening layer. Differential pulse voltammetry showed almost 100% recovery of epinephrine even in 100-fold excess of interferents. When applied to a dual glassy carbon electrode as an amperometric detector in flow injection analysis, a linear response over 0.1 μM and 10 μM was obtained. Recovery tested for 5-fold diluted human urine samples was 97.5%.</P>
Amperometric Determination of Nitrite at Poly(Methylene Blue)-Modified Glassy Carbon Electrode
Guang-Ri Xu,Guifang Xu,Ming-Lu Xu,Zhengqing Zhang,Yuan Tian,최한님,이원용 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.2
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 × 10−6 to 5.0 × 10−4 M with the detection limit of 2.0 × 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+,Ca2+, Cl−, HPO42− and H2PO4−. 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.
CUBIC B-SPLINE FINITE ELEMENT METHOD FOR THE ROSENAU-BURGERS EQUATION
Xu, Ge-Xing,Li, Chun-Hua,Piao, Guang-Ri The Youngnam Mathematical Society 2017 East Asian mathematical journal Vol.33 No.1
Numerical solutions of the Rosenau-Burgers equation based on the cubic B-spline finite element method are introduced. The backward Euler method is used for discretization in time, and the obtained nonlinear algebraic system is changed to a linear system by the Newton's method. We show that those methods are unconditionally stable. Two test problems are studied to demonstrate the accuracy of the proposed method. The computational results indicate that numerical solutions are in good agreement with exact solutions.