اندازه گيري الكتروكاتاليزي برخي تركيبات بيولوژيك با بكارگيري نانو لوله هاي كربني به عنوان سنسور و اصلاحگر آلي در سطح الكترود خمير كردن

چكيده انگليسي :

Electrocatalytic determination of some biological compounds using carbon nano tube as a sensor and organic mediator at surface of carbon paste electrode Samira Dadkhah Tehrani dadkhah samira@yahoo com Date of Submission 20 December 2010 Department of Chemistry Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Ali A Ensafi Email Ensafi@cc iut ac ir Abstract Amino acids are molecules containing an amine group a carboxylic acid group and a side chain that varies between different amino acids These molecules are particularly important in biochemistry Amino acids play central roles both as building blocks of proteins and as intermediates in metabolism Cysteine plays a key role in stabilizing extracellular proteins Tryptophan an essential amino acid is the largest of the amino acids Glutathione can also protect the cell against hypoxia toxicity mutagenicty or transformation by radiation and many carcinogens In this work we describe simultaneous determination of two amino acid L cysteine and tryptophan using a carbon nanotubes paste electrode CNPE modified with p aminophenol as a mediator in aqueous solution at a pH 6 0 Cyclic voltammetry CV differential pulse voltammetry DPV double potential step chronoamperometry and electrochemical impedance spectroscopy EIS were used to investigate the electrochemical behavior of L cysteine at a chemically modified electrode The results showed an efficient electrocatalytic activity of the electrode for the oxidation of L cyseine which leads to a reduction in its overpotential more than 0 55 V Using differential pulse voltammetry L cysteine and tryptophan in a mixture can each be measured independently from each other with a potential difference of 0 60 V The results showed that tryptophan cannot catalysis at a surface of the modified carbon nanotubes paste electrode The peaks current was linearly depend on L cysteine and tryptophen concentrations in the concentration range of 0 5 100 0 mol L 1 L cysteine and 10 0 300 0 mol L 1 tryptophan The detection limits for L cysteine and tryptophan were 0 3 mol L 1 and 5 7 mol L 1 respectively The diffusion coefficient and the rate of electro oxidation of L cysteine at the surface of p aminophenol modified carbon nanotubes paste electrode was determined 6 20 10 4 cm2 s 1 and 4 36 103 M 1 s 1 respectively for the experimental conditions The relative standard deviation RSD for ten replicated analysis of 10 0 M L cysteine was found 2 4 This method was also used for the determination of L cysteine and tryptophan in urine tablet water river serom and plasma samples by the standard addition method Cyclic voltammetry CV square wave voltammetry SWV double potential step chronoamperometry and electrochemical impedance spectroscopy EIS were used to investigate the electrochemical behavior of gluthathione GSH at a chemically modified electrode prepared by incorporating p aminophenol p AP into multi wall carbon nanotubes paste matrix The result showed that p aminophenol multi wall carbon nanotube paste electrode p APMWCNTPE had high electrocatalytic activity for glutathione It has been shown by these methods that p AP can catalyze the oxidation of glutathione in aqueous buffer solution pH 5 0 and produces a sharp oxidation peak current at about 0 21 vs Ag AgCl reference electrode The square wave voltammetric peak current of GSH increased linearly with the corresponding GSH concentration in the two linear ranges of 0 2 4 3 mol L 1 and 4 3 100 0 M with a detection limit of 0 09 mol L 1 The catalytic rate constant for oxidation of GSH at the p APMWCNTPE was also determined and found to be about 9 30 103 M 1 s 1 The diffusion coefficient of GSH was also estimated as 6 00 10 4 cm2 s 1 for the experimental conditions using chronoamperometry The relative standard deviation for ten replicated analysis of 10 0 M GSH was found 2 1 This method was also examined as a selective simple and precise new method for voltammetric This method was use

دادخواه تهراني، سميرا

اندازه گيري الكتروكاتاليزي برخي تركيبات بيولوژيك با بكارگيري نانو لوله هاي كربني به عنوان سنسور و اصلاحگر آلي در سطح الكترود خمير كردن

L- سيستين , تريپتوفان , گلوتاتيون , خمير نانو لوله ي كربني چند ديواره و پاراآمينوفنل