A Novel Carbon Paste Electrode for Potentiometric Determination of Vanadyl Ion

Carbon paste electrode was modified by disodium 2,4-diamino-7-methylbenzo[g] pteridine-5,10-dioxide to fabricate a sensor for potentiometric determination of vanadyl ion (VO2+) in aqueous medium. The new ligand was synthesized in three steps with high yield. The optimal composition of the carbon paste was made of graphite powder (64.5%), ionophore (16.6%), paraffin oil (17.8%), and sodium tetraphenylborate (NaTPB, 1.1%). The electrode exhibited a constant sensitivity of 30.20 ± 0.5 mV to VO2+ ions over a concentration range of 5 mM to 1 mM. The detection limit was calculated to be 5 mM with a response time of less than 35 s. The electrode showed to be highly reproducible over a period of 3 weeks. This sensor exhibits high selectivity to VO2+ ions and was successfully employed for potentiometric titration of VO2+ ions with EDTA.