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      Voltammetric Detection of Dopamine in Presence of Ascorbic Acid and Uric Acid at Poly (Xylenol Orange) Film-Coated Graphite Pencil Electrode

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      International Journal of Electrochemistry
      Hindawi Limited

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          Abstract

          Poly (xylenol orange) film-coated graphite pencil electrode was fabricated for the detection of dopamine in the presence of ascorbic acid and uric acid in phosphate buffer solution of pH 7. The redox peaks obtained at modified electrode shows a good enhancement. The scan rate effect was found to be a diffusion-controlled electrode process. The electrochemical oxidation of dopamine was depended on pH, and the limit of detection was found to be 9.1 × 10 −8 M. The simultaneous study gave and excellent result with great potential difference between dopamine and other bioactive organic molecules by using both cyclic voltammetric and differential pulse voltammetric techniques. The present modified graphite electrode was applied to the detection of dopamine in the injection samples, and the recovery obtained was satisfactory.

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          Probing brain chemistry with electroanalytical techniques

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            Polyeugenol-modified platinum electrode for selective detection of dopamine in the presence of ascorbic Acid.

            A platinum electrode was modified with electropolymerized films of 4-allyl-2-methoxyphenol (eugenol) by its oxidative polymerization from an alkaline solution by cyclic voltammetry. The modified electrode was than used to determine dopamine (DA) in an excess of ascorbic acid (AA) by differential pulse voltammetry. The peak positions as well as relative sensitivity DA/AA were affected by the potential window applied for the polymerization. For polymerization between 0 and 2.2 V, the peak potentials recorded in a phosphate buffer solution (pH 7.4) were -61 and +152 mV vs Ag/AgCl for AA and DA, respectively. After a 5-min equilibration, relative sensitivity DA/AA was 164 and the current sensitivity for DA was 7.9 nA μM(-)(1). The detection limit for S/N = 3 is 0.1 μM. The high selectivity and sensitivity for DA was found to be due to charge discrimination/analyte accumulation and an effect of catalytic mediation of redox sites. Chronocoulometric data reveal that DA is accumulated on the electrode as a monolayer. The electrode is stable, reversible, and free of fouling problems.
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              Electrochemical genosensor based on colloidal gold nanoparticles for the detection of Factor V Leiden mutation using disposable pencil graphite electrodes.

              Electrochemical genosensors for the detection of the Factor V Leiden mutation from polymerase chain reaction (PCR) amplicons using the oxidation signal of colloidal gold (Au) is described. A pencil graphite electrode (PGE) modified with target DNA, when hybridized with complementary probes conjugated to Au nanoparticles, responded with the appearance of a Au oxide wave at approximately +1.20 V. Specific probes were immobilized onto the Au nanoparticles in two different modes: (a) Inosine-substituted probes were covalently attached from their amino groups at the 5' end using N-(3-dimethylamino)propyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (NHS) as a coupling agent onto a carboxylate-terminated l-cysteine self-assembled monolayer (SAM) preformed on the Au nanoparticles, and (b) probes with a hexanethiol group at their 5' phosphate end formed a SAM on Au nanoparticles. The genosensor relies on the hybridization of the probes with their complementary targets, which are covalently immobilized at the PGE surface. Au-tagged 23-mer capture probes were challenged with the synthetic 23-mer target, 131-base single-stranded DNA or denatured 256-base polymerase chain reaction (PCR) amplicon. The appearance of the Au oxidation signal shortened the assay time and simplified the detection of the Factor V Leiden mutation from PCR amplified real samples. The discrimination between the homozygous and heterozygous mutations was also established by comparing the peak currents of the Au signals. Numerous factors affecting the hybridization and nonspecific binding events were optimized. The detection limit for the PCR amplicons was found to be as low as 0.78 fmol; thus, it is suitable for point-of-care applications.
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                Author and article information

                Journal
                International Journal of Electrochemistry
                International Journal of Electrochemistry
                Hindawi Limited
                2090-3537
                2011
                2011
                : 2011
                :
                : 1-8
                Article
                10.4061/2011/512692
                bef3e19a-ef21-4ecd-9182-44fb4a9d470a
                © 2011

                http://creativecommons.org/licenses/by/3.0/

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