Modification of carbon paste with congo red supported on multi-walled carbon nanotube for voltammetric determination of uric acid in the presence of ascorbic acid |
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Authors: | Saeed Shahrokhian Hamid Reza Zare-Mehrjardi Habibollah Khajehsharifi |
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Institution: | (1) Department of Chemistry, Sharif University of Technology, Tehran, 11155-9516, Iran;(2) Institute for Nanoscience and Technology, Sharif University of Technology, Tehran, Iran;(3) Department of Chemistry, Faculty of Sciences, Yasouj University, Yasouj, 75914-353, Iran |
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Abstract: | A chemically modified carbon-paste electrode (CPE) is prepared by incorporating congo red (CR) immobilized on multi-walled
carbon nanotube (MWCNT). The results show that CR is effectively immobilized on the surface of MWCNT under the ultrasonic
agitation in aqueous solution and further incorporating the nafion. The prepared electrode, due to the electrostatic repulsions
between the CR and ascorbate anion, is capable to mask the response of the ascorbic acid (AA) completely and provide an effective
method for the detection of minor amounts of uric acid (UA) in the presence of high concentrations of AA. On the other hand,
an increase in the microscopic area of the electrode by addition of MWCNT together with the electrocatalytic activity caused
to a significant enhancement in the voltammetric response to UA. Optimization of the amounts of composite modifier in the
matrix of CPE is performed by cyclic and differential pulse voltammetric measurements. The modified electrode shows a linear
response to UA in the range of 1.0 × 10−7–1.0 × 10−4 M with a detection limit of 1.0 × 10−8 M. The electrode exhibits excellent accuracies for the determination of UA in the presence of high concentrations of AA (a
recovery of 97.6%). The response of the electrode toward sulfhydryl compounds such as cysteine, penicillamine, and glutathione
is not considerable. This reveals a good selectivity for the voltammetric response toward UA. The effective electrocatalytic
property, ability for masking the voltammetric responses of the other biologically reducing agents, ease of preparation, and
surface regeneration by simple polishing together with high reproducibility and stability of the responses make the modified
electrode suitable for the selective and sensitive voltammetric detection of sub-micromolar amounts of UA in clinical and
pharmaceutical preparations. |
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Keywords: | Carbon-paste electrode Chemically modified electrode Congo red Multi-walled carbon nanotube Uric acid Ascorbic acid |
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