New lead (II) selective membrane potentiometric sensors based on chiral 2,6-bis-pyridinecarboximide derivatives Saad S.M. Hassan a, *, M.H. Abou Ghalia b , Abdel-Galil E. Amr b , Ayman H.K. Mohamed a a Department of Chemistry, Faculty of Science, Ain Shams University, Cairo, Egypt b National Research Center (NRC), Dokki, Cairo, Egypt Received 23 September 2002; received in revised form 28 December 2002; accepted 10 January 2003 Abstract New membrane sensors with cylindrical configuration for lead (II) ions are described based on the use of three newly synthesized pyridine carboximide derivatives as neutral ionophores in plasticized PVC membranes. The sensors exhibit significantly enhanced response towards lead (II) ions over the concentration range 4 /10 6  /1 /10 2 mol l 1 at pH 4.5  /7 with a lower detection limit of 0.4  /3.7 mg ml 1 . The sensors display near-Nernstian slope of 26.0  /33.1 mV per decade for Pb(II) ions. Effects of plasticizers, lipophilic salts and various foreign common ions are tested. The sensors show long life span, good selectivity for Pb(II) over a wide variety of other metal ions, long term stability, high reproducibility, and fast response. Validation of the method by measuring the lower detection limit, range, accuracy, precision, repeatability and between-day-variability reveals good performance characteristics of the proposed sensors. The sensors are used for direct determination of lead in stack emissions of lead smelters, assay of lead in rocks and monitoring of potentiometric titration of Pb(II) with EDTA. The results obtained agree fairly well with data obtained by atomic absorption spectrometry. # 2003 Elsevier Science B.V. All rights reserved. Keywords: Determination of lead; 2,6-Bis-pyridinecarboximide ionophores; PVC membrane; Potentiometric sensors 1. Introduction Many cyclic and acyclic macromolecules have been recently introduced as ionophores in poten- tiometric and optical polymeric membrane sensors for various cations and anions. Crown ethers [1  / 3], polyamines [4], calixarenes [5], metalloporphyr- ines [6], RNA [7], and metallocenes [8] have been shown to bind some organic and inorganic cations and anions reversibly and selectively and are used as ionophores in various sensors. Dioxamides [9,10], 3,6-dioxaoctanedithioamide [11], monobis and pentakis derivatives of p -tert -butyl calixarene [12,13], calixarene phosphine oxide derivatives [14], piroxicam [15], 1,10-dibenzyl-1,10-diaza-18- crown-6 [16], dicyclohexano-18-crown-6 tetra- kis(2-pyridylmethyl)ethylenediamine and diaza- * Corresponding author. Tel./fax:  /20-2-682-2991. E-mail address: saadsmhassan@yahoo.com (S.S.M. Hassan). Talanta 60 (2003) 81  /91 www.elsevier.com/locate/talanta 0039-9140/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0039-9140(03)00038-9