Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/88876
Type: Capítulo de livro
Title: A Voltammetric Sensor Based On A Hemin Modified Multiwalled Carbon Nanotube For Hydroquinome Determination In Pharmaceutical Samples
Author: Clausen D.N.
Duarte E.H.
Pereira A.C.
Kubota L.T.
Tarley C.R.T.
Abstract: A simple, low cost and sensitive electrochemical method for the detection of hydroquinone (HQ) was developed based on a carbon nanotube paste (70%) electrode modified with hemin (20%) and mineral oil (10%). The aim of the present work was to evaluate the performance of a hemin (iron(II) protoporphyrin IX) functionalized carbon nanotube sensor for the voltammetric determination of HQ. The modified electrode demonstrated an electrocatalytic activity for the HQ oxidation in a 0.05 M Tris-HCl buffer solution (pH 7) using cyclic voltammetry. The anodic peak current of the sensor was 4 and 2.8 times higher when compared to glassy carbon and non-modified carbon nanotube paste electrodes, respectively. The best paste composition was found to be 3.5:1 (MWCNT:Hemin), considering the smaller separation between the cathodic and anodic peaks (ΔE) as well as the larger peak currents. The linear plot of anodic peak current vs. square root of scan rate demonstrated that the HQ oxidation was a diffusion-controlled process. The square wave parameters were optimized, and the best results obtained were as follows: amplitude = 70 mV, frequency = 70 Hz, and step of potential = 0.01 V. 0.15 mol L-1 Tris-HCl was found to be the best buffer solution condition. The analytical curve was linear in the HQ concentration range of 2.5 - 120 μmol L-1 (r = 0.9962, sensitivity = 0.14507 μA μmol L-1, and precision = 2 %). The limits of detection and quantification for HQ were estimated to be 0.78 μmol L-1 and 2.60 μmol L-1, respectively. The evaluation of HQ as electron mediator had insignificant effects on the sensing mechanism, showing that the proposed sensor did not act like a second-generation electrode. Therefore, peroxide was not used to measure HQ amounts. The HQ diffusion coefficient was found to be 6.34x10-5 cm2 s-1. The proposed method presented no significant differences at the 95 % confidence level compared to the chromatographic method. It can be employed for detecting other phenolic compounds, such as guaiacol, catechol, N-acetyl-p-aminophenol, ascorbic and uric acids; besides, it can be applied to pharmaceutical formulations. © 2013 by Nova Science Publishers, Inc. All rights reserved.
Editor: Nova Science Publishers, Inc.
Rights: fechado
Identifier DOI: 
Address: http://www.scopus.com/inward/record.url?eid=2-s2.0-84895346183&partnerID=40&md5=28bc60c5c7d663996a16e98173a2bf28
Date Issue: 2013
Appears in Collections:Unicamp - Artigos e Outros Documentos

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