Determination of ultratrace levels of lead (II) in water samples using a modified carbon paste electrode based on a new podand

A new podand of 1,1′-thiobis(naphthalene-2,1-diyl)bis(2-aminobenzoate) (TNBA) was synthesized and used as a suitable carrier for construction of Pb2+ modified carbon paste electrode (CPE). The effects of various plasticizers; 2-nitrophenyloctylether (o-NPOE), dioctyl pththalate (DOP), dibutyl phthalate (DBP) and paraffin oil were studied. The best performance was obtained with a matrix composition of CPE with a DOP/graphite powder/TNBA weight percent ratio of 35/60.5/4.5. The sensor exhibits significantly enhanced selectivity toward Pb2+ ion over the concentration range 8.0 × 10− 8 to 1.0 × 10− 2 mol L− 1 with a lower detection limit of 5.0 × 10− 8 mol L− 1 and a Nernstian slope of 29.0 ± 0.2 mV decade− 1 of lead activity. It has a fast response time of 8 s with a working pH range from 3.5 to 7. The interaction between TNBA and Pb2+ was studied spectrophotometrically and it exhibits that the stoichiometry of the complex is 1:1 in acetonitrile solution. Finally, the electrode was satisfactorily used as an indicator electrode in complexometric titration of Pb2+ with EDTA and in direct determination of lead in various water samples.