A Novel Potentiometric Sensor Based on 1,2-Bis(N'-benzoylthioureido)benzene and Reduced Graphene Oxide for Determination of Lead (II) Cation in Raw Milk

We have developed a highly sensitive and selective potentiometric PVC-membrane sensor for lead (II) cation. A glassy carbon electrode (GCE) was modified with synthesized 1,2-Bis(N'-benzoylthioureido) benzene (BBTB) as an ionophore and reduced graphene oxide (RGO), and this material was characterized by scanning electron microscopy. The sensor shows sensitive and highly selective response to Pb(II) ion with a linear range from 6.31 × 10−8 to 3.98 × 10−2 M, Nernstian slope of 30.37 ± 0.62 mV per decade and a detection limit of 2.51 × 10−8 M. The proposed sensor could be used in a pH range of 4.0-8.0. Selectivity coefficients were determined for known common cations by applying the match potential method (MPM). The sensor was successfully applied to monitor Pb(II) in raw milk and in potentiometric titration of Pb2+ ions. The structure of BBTB ligand and its complexation with some common cations were investigated by using quantum mechanical DFT calculations. Lead (II) cation showed prominent affinity to the BBTB carrier.