Electrocatalytic oxidation of hydroxylamine at a rutin multi-wall carbon nanotubes modified glassy carbon electrode: Improvement of the catalytic activity

A highly sensitive sensor for the determination of hydroxylamine was described. It consists of a rutin multi-wall carbon nanotubes (RMWCNT) modified glassy carbon electrode (GCE). The cyclic voltammograms of the modified electrode indicated that the surface confined rutin were strongly dependent on the solution pH, as anticipated for quinone/hydroquinone functionalities. The RMWCNT modified GCE exhibited catalytic activity toward the electro-oxidation of hydroxylamine. The results show that there is a dramatic enhancement of the anodic peak current of hydroxylamine oxidation at RMWCNT modified GCE relative the value obtained at the rutin modified GCE (RMGCE) or activated GCE (AGCE). In other words the combination of MWCNT and mediator (rutin here) definitely improve the characteristics of hydroxylamine oxidation. The kinetics parameters such as the electron transfer coefficient, alpha, the heterogeneous rate constant, k', and the standard heterogeneous rate constant, k(0), for the electro-oxidation of hydroxylamine at the RMWCNT modified GCE were determined using RIDE voltarnmetry. The results show k' are strongly potential dependent and increase with increasing the potential which considering for drawing the Koutecky-Levich plot. In amperometric measurements at a RMWCNT modified electrode during the addition of even 1.0 mu M hydroxylamine, a well-defined response was observed. The plot of electrocatalytic current versus hydroxylamine concentration is constituted from two linear segments, corresponding to two different range of 1.0-33.8 and 33.8-81.7 mu M. Finally, it was found that the relative standard deviation of amperometry current of 10.0 [mu M hydroxylamine for 15 replicate determinations is 2.6%. (C) 2007 Elsevier B.V. All rights reserved.