Multiwall Carbon Nanotubes Modified Carbon Paste Electrode for Determination of Copper(II) by Potentiometric and Impedimetric Methods

A chemically modified carbon paste electrode with multiwall carbon nanotube (MWCNT) was prepared and used as a sensor for Cu2+  ion. The unique chemical and physical properties of CNT have paved the way  to  new  and  improved  sensing  devices.  A  central  composite chemometrics  design  was  applied  for  multivariate  optimization  of the  effects  of  three  significant  parameters  (Graphite  powder  (X1), MWCNT  (X2)  and  Ionophre  (X3))  influencing  the  response  of  the electrode.  In  the  optimized  conditions,  the  electrode  exhibits  a Nernstian  slope  of  30.1  mV/decade  in  a  linear  range  between 1.0×10-6   to1.0×10-1  M over a wide pH range (2.0-6.5). Importantly, the  effect  of  the  MWCNT  on  the  performance  of  electrode  was investigated  by  impedance  technique,  that  showed  the  MWCNT helps the transduction of the signal in carbon paste electrode and the charged  transfer  resistance  (Rct)  was  reduced.  The  impedimetric results indicated that the linear concentrations range was 1.0×10−7  to 1.0×10−1  M  and  in  comparison  with  potentiometry,  the  pH  range increased to 2.0−7.5.