Synthesis, Characterization and Pb(II) Ion Selectivity of N, N′- bis(2-hydroxy-1-napthalene)-2,6-pyridiamine (BHNPD)

N,N′-bis(2-hydroxy-1-napthalene)-2,6-pyridiamine (BHNPD)(I) has been synthesized by the reaction of 2,6-diaminopyridine with 2-hydroxy-1-napthaldehyde at 60 oC in methanol. The BHNPD (I) was characterized by FT-IR, 1H NMR and elemental analyzer (C, H, N). PVC-based membranes of BHNPD (I) were prepared and investigated for response toward Pb2+ ions. The best performance was obtained for the membrane of composition (BHNPD) (I): PVC: NaTPB: NPOE in the ratio 3:120:2:150. The sensor shows a linear potential response for Pb2+ over wide concentration range 3.2 x 10-6 - 1.0 x 10-1 M with Nernstian compliance (29.1 mV decade-1 of activity) between a wide pH range (3.5-7.5) and a fast response time of 10 s. This sensor can also be used in partially non-aqueous media having upto 20 %(v/v) methanol, ethanol or acetone content with no significant change in the value of slope or working concentration range. The selectivity coefficient values are in the range of 1.0 x 10-2 to 1.0 x 10-4 for mono-, bi-, and trivalent cations and anions, which indicate good selectivity for Pb2+. The sensor has a lifetime of six months and could be used as an indicator electrode in the potentiometric titration of Pb2+ vs. EDTA and also in the estimation of lead in waste water.