Copper nanoparticle modified carbon electrode for determination of dopamine
Introduction
Recently improvement of life quality becomes an important objective of the researches. The quality of life is directly related to the control of food quality and safety, and quality of drinking water. In all these fields continuous, fast and sensitive monitoring of many various chemical and biological materials is required. Some mentioned analytical problems could be solved using particular electrochemical methods with application of modified electrodes [1], [2]. Since, modified electrodes enable to increase the selectivity of electroanalytical processes, which could be not achieved using bare electrodes [3], [4] for this reason the modification of carbon-based electrodes by highly ordered mono- or multi-layer deposition can significantly increase their analytical applicability [5], [6], [7]. To enhance chemical functionality of carbon surface, electrochemical oxidation of amine-containing compounds, aryl acetates or aliphatic alcohols [8], electrochemical reduction of diazonium salts [9], electrochemical deposition of conducting and non-conducting polymers [10] have been applied. On the other hand, it has been noticed that metal and metal oxide nanoparticles represented excellent electronic and electrocatalytic properties, which accelerates the rate of heterogeneous electron exchange between the electrode surface and some species present in the solution [11], [12]. For this reason, recently for the modification of carbon surfaces, a wide range of nanoparticles was applied in some researches [13], [14], [15]. Electrodes modified with gold, platinum, palladium, copper, nickel, and silver nanoparticles have revealed good performances in catalysis, facilitation of mass transport, increase of effective surface area [16], [17], [18]. The researches based on application of gold nanoparticles have been the most widely performed [19], [20], [21]. However compared with noble metal nanoparticles, the copper nanoparticles are much cheaper. Therefore the studies related to preparation and application of copper nanoparticle-modified electrodes are very important [11], [13], [22].
Dopamine, which is also known as 3,4-dihydroxyphenylethylamine is an important neuro-transmitter and it is widely distributed in mammalian central nervous system. Low levels of dopamine are related to neurological disorders such as schizophrenia, Parkinson's disease and human immunodeficiency virus infection [23], [24], [25]. For this reason recently, a variety of analytical techniques has been proposed for determination of dopamine in biological samples [26], [27], [28]. Dopamine is electrochemically active therefore; electrochemical detection methods could be applied for the determination of this compound. However in biological samples electrochemical determination of dopamine is usually interfered by ascorbic acid, for this reason the selectivity of electrochemical sensors required for dopamine determination in biological samples is important [24], [29], [30]. To solve this problem electrode modification with self-assembled monolayer, gold nanoparticles, carbon nanotubes conducting and/or electrochemically generated polymers have been applied [24], [25], [27], [30], [31].
In this research the development of highly sensitive and selective dopamine sensor based on copper nanoparticles (CuNPs) as recognition element is presented. We illustrated that such sensor can be used for the selective determination of dopamine even in the presence of high concentrations of interfering materials such as ascorbic acid, uric acid, and p-acetamidophenol.
Section snippets
Reagents and apparatus
100 mM phosphate buffer solution (PBS) of different pH values were prepared by mixing four stock solutions of H3PO4, KH2PO4, K2HPO4, and K3PO4. The Britton–Robinson (BR) buffer was prepared by mixing main stock solutions or solids of H3BO3, H3PO4, CH3COOH, and KCl. All chemicals for preparation of BR buffer and phosphate buffer saline (PBS) were of extra pure grade and were purchased from Merck Ltd. (Darmstadt, Germany). All other chemicals used in this study were of analytical grade and were
Results and discussion
This research was focused on the application of CuNPs in order to improve sensitivity and selectivity of GC electrodes toward dopamine. For this aim, CuNPs were synthesized and characterized by SEM and TEM. SEM image is presented in Fig. 1A. As it is seen from SEM image CuNPs appeared spherical and tended to aggregate. The average size of CuNPs is approximately 40 nm. In addition, TEM image of synthesized nanostructures is presented in Fig. 1B. Similarly to SEM image CuNPs of spherical shape and
Conclusions
CuNP/GC electrode proposed in this study showed high electrochemical activity toward dopamine. It was demonstrated that accurate determination of dopamine is possible even in the presence of ascorbic acid, uric acid, and p-acetamidophenol even if concentrations of these compounds exceeded the concentration of dopamine by 100 times. Positive indications let us to predict that proposed method could be applied for the determination of dopamine in real samples. Moreover some analytical
Acknowledgement
This work was partially supported by the first term International Postdoctoral Research Scholarship Project of The Scientific and Technological Research Council of Turkey in 2011.
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