Response Surface Optimization of MWCNT modified Carbon Paste Electrode for Zn(II) Determination

A novel carbon paste electrode based on 3,7,12,17-Tetramethyl-8,13-divinyl-2,18-porphinedipropionic acid disodium salt (Ionophore) modified with multi-walled carbon nanotube (MWCNT) is fabricated for the selective determination of Zn2+. Central composite design (CCD) and response surface methodology is used in this work to study the effect of different independent variables and to optimize the variable for a particular response. Five variables namely, ionophore, MWCNT, sodium tetraphenylborate, paraffin oil and graphite were studied in a 33 experiment CCD. The slopes of the calibration graphs were measured as the response of the electrode. A mathematical model equation was obtained from computer simulations from the optimization studies. The optimized electrode showed a linear range of 1.0x10(-1) to 3.15x10(-7) M and a detection limit of 2.5x10(-7) M. The response time of the electrode was found to be 20 s and a slope of 30.73 +/- 0.81 mV/decade. The electrode showed a good selectivity for Zn2+ relative to many cations. Potentiometric titration was used to study the analytical application of the electrode. The optimized electrode was effectively used for the titration of Zn2+ with EDTA.