Electrodeposition of carboxylated multiwall carbon nanotubes on graphite reinforcement carbon for voltammetry detection of cadmium

Abstract

Determination of cadmium ion at trace and sub-trace levels is still challenging due to high cost and limited capability of analytical instrumentation. A simple, low cost, non-toxic graphite reinforcement carbon (GRC) electrode modified with carboxylated multiwall carbon nanotubes (c-MWCNT) was prepared by electrodeposition process and used for the determination of cadmium ions at sub-part per billion (sub-ppb) levels. The study involved investigation of electrochemical performance of GRC with different hardness and size. The carboxylated-functionalized MWCNT was characterized by Fourier Transform Infrared Spectrophotometer (FTIR) and Field Emission Scanning Electron Microscope-Energy Dispersive X-ray analysis (FESEM-EDX). FESEM was also used to investigate the surface morphology of the c-MWCNT/GRC electrode. The newly developed electrode was successfully used for the detection of cadmium ion in 0.04 M Briton Robinson Buffer (BRB) by differential pulse anodic stripping voltammetry (DPASV). Some important operational parameters including pH of the buffer, initial potential, scan rate and accumulation time were optimised. Optimum conditions for the DPASV technique was obtained as follows: initial potential Ei = -1600 mV vs. Ag/AgCl (satd.); scan rate ? = 2 mV per sec.; pH = 5.0; deposition time of 10 sec. Based on the DPASV of cadmium ion peak height at -0.78 V vs. Ag/AgCl (Sat’d), the c-MWCNT was found to enhance the anodic peak current of cadmium ion by a factor of 7 fold compared to that peak produced using a bare GRC electrode. Linear calibration curves were obtained from 1 ppb to 5 ppb with detection limit of 0.004 ppb and limit quantification of 0.012 ppb (R2=0.966) respectively. The results suggest that the newly developed c-MWCNT/GRC has a potential to be a simple, efficient, low cost and disposable electrode system for the determination of cadmium ions at a very low concentration level.