Talanta 76 (2008) 454–457 Contents lists available at ScienceDirect Talanta journal homepage: www.elsevier.com/locate/talanta Amperometric detection of carbohydrates and thiols by using a glassy carbon electrode coated with Co oxide/multi-wall carbon nanotubes catalytic system Susanna Buratti ∗ , Barbara Brunetti, Saverio Mannino Department of Food Science and Technology, University of Milan, Via Celoria 2, 20133 Milan, Italy article info Article history: Received 23 November 2007 Received in revised form 10 March 2008 Accepted 21 March 2008 Available online 28 March 2008 Keywords: Carbohydrates Thiols Carbon nanotubes Cobalt oxide Amperometric detection abstract A glassy carbon electrode coated with cobalt oxide/multi-wall carbon nanotubes (MWCNT) system was used for the detection of carbohydrates and thiols. The modification of the glassy carbon electrode increased the anodic current response of these organic compounds and decreased their overvoltage. The amperometric responses were extremely stable with no loss of sensitivity over many days of storage. Such attractive performance characteristics indicate great promise for using this new catalytic system for mon- itoring in fast and simple way compounds of great interest for food industry, biotechnology and clinical diagnostics. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Carbohydrates and thiols are of great interest in many sci- entific and industrial areas and also in clinical diagnostics. The electrochemical detection of these compounds is a challenge since their direct oxidation is generally hampered by poor voltammetric behaviour at glassy carbon electrode. The main problem inherent to such anodic detection is the large overvoltage encountered for oxidation at ordinary electrodes; consequently considerable effort has been devoted toward the goal of identifying new electrode materials that will reduce the overpotential for carbohydrates and thiols oxidation. Chemically modified carbon electrode contain- ing cobalt oxide, cobalt-phthalocyanine or ruthenium dioxide have been used for amperometric measurements of sugars [1–4]; also transition metal electrodes such as copper and nickel have been employed for carbohydrates evaluation [5,6]. Electrodes modified with phthalocyanine derivatives [7–9], organic mediators [10,11] and enzyme [12], have been used for voltammetric and amper- ometric detection of thiols. Actually in the scientific community there is a great interest to explore application of carbon nan- otubes (CNTs) because of their high electrical conductivity, high surface area and good chemical stability. Several authors have ∗ Corresponding author. Tel.: +39 02 50319217; fax: +39 02 50319061. E-mail address: susanna.buratti@unimi.it (S. Buratti). reported the excellent electrocatalytic properties of multi-wall carbon nanotubes (MWCNTs) and single-wall carbon nanotubes (SWCNTs) in the electrochemical oxidation of molecules and biomolecules such as NADH [13], dopamine and ascorbic acid [14], hydrogen peroxide [15] and also carbohydrates [16,17] and thiols [18,19]. Furthermore it has been shown that the combina- tion of CNT with glucose oxidase [20] or copper [21], provide a mean of enhancing the detection of glucose and sugars in gen- eral. Although some works have been published on electrosorbtion or adsorption of phthalocyanines and metallophthalocyanines on CNT [22–24] there are no works about glassy carbon electrodes modified with MWCNT and cobalt. This article reports an easy preparation method of Co oxide/multi-wall carbon nanotubes catalytic sys- tem and a fast procedure to modify glassy carbon electrode. The Co oxide/MWCNT system was prepared according to the work of Liu et al. [25]. In that work high resolution transmission electron microscopy (HRTEM) was used for investigate the microstructure of cobalt nanoparticles formed on MWCNTs surface and it has been demonstrated that cobalt nanoparticles deposited on oxidized MWCNTs gave rise to a monometallic system that exhibited high catalytic activity. The electrocatalytic activity of the proposed electrode was eval- uated towards the detection of carbohydrates and thiols in a flow injection system. In the following sections we well demonstrate that Co oxide/MWCNT catalytic system display a great promotion 0039-9140/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2008.03.031