Amino Acid Modified Glassy Carbon Electrode And Application In Drug Analysis

1. Voltammetric Determination of Adenine in Pharmaceutical Formulation at Poly-L-Cysteine Modified Glassy Carbon ElectrodeA simple and reliable method based on the electropolymerized L-cysteine film modified glassy carbon electrode for the determination of adenine was described. The modified electrode showed strong electrocatalytic activity towards the oxidation of adenine. After accumulation on pretreated poly-L-cysteine/GCE at the potential of-0.2 V for 300 s, the peak current obtained at + 0.993 V. Increased linearly dependent on the adenine concentration and Vitamin B4 tablet in the range of 2.0×10^-7 M～1.0×10^-4 M and 1.0×10^-6 M～1.0×10^-4 M in phosphate buffer solution (0.1 M, pH 6.0). The low-cost modified electrode showed good sensitivity, selectivity, stability and less interference by guanine. The proposed method was successfully used for the estimation of the adenine contents in Vitamin B4 and simulation samples with satisfactory results. The electrochemical reaction mechanism of adenine was also discussed.2. Selective Determination of Dopamine in The Presence of Ascorbic Acid at the Poly-L-arginine Modified ElectrodeA method for the determination of dopamine was described. The determination at the sensor was prepared by modifying a glassy carbon electrode (GCE) surface with poly-L-arginine. Dopamine could be accumulated on the L-arginine modified electrode by the electrostatic interaction. The modified electrode showed strong electrocatalytic activity towards dopamin. The catalytic peak current obtained at + 0.158 V (vs.SCE) from DPV was linearly dependent on the dopamine concentration in the range of 1.96×10^-5 M 1.38×10^-7M in the PBS (0.1 M, pH 7.5) with a correlation coefficient of 0.999. The detection limit (S/N=3) was 2.0×10^-8 M. The modified electrode showed good sensitivity, selectivity, stability and less interference from ascorbic acid. Keywords: L-Cysteine; Adenine; Glassy Carbon Electrode3. Trace quercetin detectionbased on iron tetrasulphonated phthalocyanine/poly-l-lysine film modified glassy carbon electrodeThe iron tetrasulphonated phthalocyanine/poly-l-lysine has been modified on the electrode for the sensitive determination of quercetin. It was prepared by modifying a glassy carbon electrode (GCE) surface with a iron tetrasulphonated phthalocyanine (FeTSPc) during the polymerization of poly-l-lysine (PLL) film on the electrode. The modified electrode showed strong electrocatalytic activity towards the oxidation of quercetin. Quercetin produced well-defined oxidation peaks at about + 0.252 V (vs. SCE). Using amperomatric method, the linear range for the determination of quercetin was 4.0×10^-7 M～1.0×10^-5 M, and the detection limitation was down to 4.0×10^-8 M. This proposed method has also been successfully used for the estimation of the quercetin concentration in the simulation samples.