Synthesis and Application of New Porphyrin Derivatives for Preparation of Copper Selective Electrodes: Influence of Carbon Nanotube on Their Responses

The synthesis and characterization of 5-(4- benzylacrylamide)-10, 15, 20-tris(4-benzylamine)porphyrin ((BAmidBAmin)P) and poly[5-(4-benzylacrylamide)-10, 15, 20-tris(4-benzylamine)porphyrin] (P[(BAmidBAmin)P]) are reported in this paper. The techniques IR, 1 H-NMR, UV-Vis and elemental microanalysis were used to characterize the porphyrins. These new compounds were used to manufacture a new carbon paste selective electrode for the measurement of copper ions in real samples. The effects of the carriers, sodium tetraphenylborate (NaTPB), multiwalled carbon nanotube (MWCNT), and Nujol on the electrode response were studied. The optimum values for (BAmidBAmin)P electrode were obtained as follows: carbon (150 mg), NaTPB (1.8 mg ), Nujol (36 mg), carrier (7 mg), and MWCNT (15 mg); and the optimum values for P[(BAmidBAmin)P] electrode were found to be 150, 3, 30, 7, and 20 mg, respectively. At the optimal conditions, the responses of the electrodes are linear in the Cu²⁺ concentration of 5.0 × 10^-9 - 1.0 × 10^-1 mol/L for (BAmidBAmin)P electrode and 1.0 × 10^-8 - 1.0 × 10^-1 mol/L for P[(BAmidBAmin)P] electrode. Moreover, the Nernstian slopes for (BAmidBAmin)P and P[(BAmidBAmin)P] electrodes were 29.50 ± 1.00 and 29.84 ± 1.00 mV per decade^-1, respectively. The advantages of these electrodes include a low detection limit (4 × 10^-9 and 8.5× 10^-9 mol/L, wide pH range (2.5-5.5), short response time (~2 s) and high lifetime (3 months) for both carriers.