Utilização de fibras de carbono como material eletrodico na construção de sensores e biossensores

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

This thesis describes the use of carbon fibres as electrodic material for the construction of sensors and biosensors. Although carbon fibres have several advantages as electrodic material, their pre-treatment is necessary in order to enhance reproducibility and electrochemical activity. A simple and fast method for its activation is proposed to improve the electrochemical activity of the carbon fibre electrodes. The carbon fibre surface was coated with a layer of titanium (IV) oxide. The fibre was treated for 1h at room temperature with TiCI4, followed by hydrolyzation of the remaining chloride and, finally dried. The titanium oxide layer dispersed onto the carbon fibre surface was very stable and a sharp improvement in the electrochemical response was observed. The electrochemical response for hexacyanoferrate was similar to that observed for reversible systems. The treated fibres were used to construct sensors for simultaneous determination of phenol isomers, using multivariate calibration to model the overlapped peaks obtained by differential pulse voltammetry .The best condition for electrochemical response was obtained with 0.05 mol LTris- HCL buffer, at pH 6.0. Initially the voltammograms were processed using a Fourier transform filter and PCA for noise reduction and data compression, respectively. For hydroquinone, the result obtained with neural network was slightly better than with the PLS1 and PLS2. However, similar errors were obtained for catechol when using either PLS or the neural network models. Using the neural network with pruning, it was possible to determine catechol and hydroquinone in the concentration range of 1.0 10 to 6.0 10 mol L, with standard errors of predictions (%PMSEP) of 7.42 and 8.02, for catechol and hydroquinone, respectively. Biosensors for salicylate were constructed by salicylate hydroxilase (SH) immobilisation on different carbon fibres. The characteristics of the microbiosensors prepared with different carbon fibres were investigated. The carbon fibre (Toray- T800) resulted in the best amperometric biosensor for salicylate detection. It showed linear response range between 0.10-1.93 mmol L and 1.96 -12.0 mmol L, a detection limit of 5.57 10 mol L and a response time of 3.5 s. The high sensitivity was attributed to the chemical amplification process on the electrode surface. The determination of salicylate can be carried out applying potentials higher than 150 mV, with good precision. The useful lifetime of the biosensor was at least 100 continuous determinations without significant change. The results with clinical and pharmacological samples were statistically equal in 95% of confidence level, when compared with Trinder method.

ASSUNTO(S)

biosensores carbono detectores

ACESSO AO ARTIGO

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