Construction of a Fe3+ Carbon Paste Electrode Based on Multi-walled Carbon Nanotubes (MWCNTs)/Nanosilica

The results of our previous studies showed a selective interaction between Di-tertbutylazodicarboxylate (TBADC) and Fe3+ ions respect to other metal ions. A new carbon paste ion selective electrode for determination of iron amount was prepared. Using multi-walled carbon nanotube (MWCNT) and nanosilica in the composition of carbon paste electrodes (CPEs) cause improvement in their characterizations. The best performance for nano-composite sensor was obtained with electrode composition of 4% TBADC, 0.3% nanosilica, 30% paraffin oil (binder), 62.7% graphite powder, and 3% MWCNT. The new Fe3+-CPE showed a Nernstian slope of 19.9 +/- 0.4 mV per decade with a detection limit of 8.0x10(-10) mol L-1 in the range of 1.0x10(-9)-1.0x10(-2) mol L-1. The sensor could be used in a pH window of 1.6-4.3 and the response time of the sensor was at least 5 s, in addition to its very good Fe3+ selectivity over many mono-, di-and trivalent transition and heavy metal ions. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of 25 mL of a 10x10(-2) mol L-1 Fe3+ ions with a 10x10(-4) mol L-1 EDTA and the monitoring of the Fe(III) concentration ions in some cationic mixtures.