American Journal of Analytical Chemistry, 2011, 2, 814-819 doi:10.4236/ajac.2011.27093 Published Online November 2011 (http://www.SciRP.org/journal/ajac) Copyright © 2011 SciRes. AJAC Multiwall Carbon Nanotube Modified Electrochemical Sensor for Reactive Black 5 Velliangiri Sreeja 1 , Raman Sasikumar 2 , Marimuthu Alagarsamy 2 , Paramasivam Manisankar 2* 1 Vellalar College for Women (Autonomous), Tamil Nadu, India 2 Department of Industrial Chemistry, Alagappa University, Tamil Nadu, India E-mail: * pms11@rediffmail.com Received July 18, 2011; revised August 19, 2011; accepted August 29, 2011 Abstract Cyclic voltammograms of reactive black5 (RB5) at different pHs in the range 1.0 - 13.0 on multiwall carbon nanotube modified glassy carbon electrode revealed the presence of one well-defined irreversible anodic peak around 975 mV in acidic and neutral pHs. Adsorption controlled oxidation observed at acidic pH 1.0 resulted in the maximum peak current response in cyclic voltammograms. A systematic differential pulse stripping voltammetric studies were carried out using the modified electrode at pH 1.0. The accumulation parameters, accumulation potential and time were optimized for maximum adsorption of the dye which was ascertained from the SEM photographs and XRD results. The stripping parameters were optimized and cali- bration was made under optimum conditions. The range of study was from 0.5 ppm to 100 ppm and the lower limit of determination was 100 ppm. Five identical experiments were carried out and the RSD value obtained was 2.5% suggesting good reproducibility. The proposed method was successfully applied to de- termine the concentration of dye in the fabric and wastewater after dyeing. Keywords: Cyclic Voltammetry, Reactive Black 5, Stripping Voltammetry, Multiwall Carbon Nanotubes 1. Introduction An important milestone in the history of carbon materials is the discovery of carbon nanotubes (CNTs) [1] having two distinct types of structures namely single walled and multiwalled. As a consequence of the excellent electro- nic and conducting properties of CNTs, electrodes modi- fied with CNTs have demonstrated to improve the elec- troanalytical performance of different species. Due to their uniqueness, CNTs have received enormous atten- tion for the preparation of electrochemical sensors as it was extensively reviewed [2-5]. The subtle electronic behavior of CNTs reveals that they have the ability to promote electron-transfer reaction when used as electro- de materials. Recently CNT film coated electrodes have received increasing attention in analytical studies [7-9]. However a major barrier for developing the CNT modi- fied electrode is the insolubility of CNTs in usual media [10] and many efforts have been made to disperse CNTs into suitable solvents such as DMF [11], acetone [12] and concentrated sulphuric acid [13]. Yuan-hai Zhu et al. [14] functionalized MWCNTs using nitrating mixture and neutralized with dil. NaOH. The modified MW- CNTs were water soluble and used for the determination of phenylephrine. In recent days, a noncovalent method [15] has been developed and ported for solubilizing MWCNTs functionalized with Congo red. Surfactants are a special kind of amphiphilic molecules, which can spontaneously adsorb at the interfaces or assemble into micelles in solutions, forming various regulated struc- tures at electrode surfaces or in solutions. This resulted in extensive applications in electroanalysis [16]. MWC- NTs modified electrodes fabricated in the presence of surfactants resulted in high sensitivity and selectivity. MWCNT/GCE modified electrode fabricated in the pre sence of SDS exhibited enhanced sensing of organic po- llutants [17,18]. Hence the present work, we used anionic surfactant, sodium dodecyl sulphate (SDS) to disperse MWCNTs. Reactive dyes are the main group of dyes used in the textile industry [19]. They are very effective in fabric dyeing due to the reactive groups capable of forming co- valent bonds with a hydroxyl or amino group on the fiber. Inefficiency in the dyeing process resulted in 10% - 15% of all dyestuff being lost directly to wastewater [20]. Billions of kilograms of dyes are produced per annum