Available online at www.derpharmachemica.com Scholars Research Library Der Pharma Chemica, 2010, 2(6):8-18 (http://derpharmachemica.com/archive.html) ISSN 0975-413X 8 www.scholarsresearchlibrary.com Spectrometric determination of Pb 2+ cation after selective bulk liquid membrane transport using benzo-18-crown-6 as carrier Elham Fahmideh-Rad, Gholam Hossein Rounaghi*, Mohammad Hossein Arbab-Zavar, Mahmud Chamsaz Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran ______________________________________________________________________________ ABSTRACT Benzo-18-Crown-6 (B18C6) was used as a highly selective and efficient carrier for the transport of Pb 2+ cation through a dichloromethane bulk liquid membrane (BLM). In order to achieve the highest transport efficiency of Pb 2+ cation across the bulk liquid membrane system, the influence of different parameters on Pb 2+ cation transport was investigated. This includes the nature of various organic solvents as liquid membrane phase, concentration of B18C6 in the membrane phase, concentration of picric acid as counter anion in the source phase, type of various stripping agents in the receiving phase, concentration of thiosulfate ion as a suitable stripping agent in the receiving phase, pH of the source and receiving phases and equilibrium time of transport which were optimized. In the optimum procedure conditions, the transport of a 1×10 -4 M solution of Pb 2+ cation was observed (88.0 ± 0.7%) after 4 hours. The selectivity and efficiency of Pb 2+ cation transported from aqueous solutions containing equimolar mixtures of Cr 3+ , Co 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Ag + metal cations were investigated. Keywords: bulk liquid membrane (BLM), transport, Benzo-18-Crown-6 (B18C6), Pb 2+ cation, DCM. ______________________________________________________________________________ INTRODUCTION Pb 2+ is a toxic heavy metal cation that accumulates in soil and natural waters. Devices that will detect this metal at the trace level are the aim of numerous research groups. Crown ethers and, in particular, 18-Crown-6 have emerged as a potential recognition element in these devices for Pb 2+ detection. Crown ethers are known to bind selectivity to cations based on macrocycle effect [1]. Selective transport of cationic substrates by membrane carriers is of great importance in chemistry, biology and separation sciences. Bulk liquid membrane is one of the simple and efficient types of liquid membranes [2]. In this technique similar to liquid membrane configurations, (vis ion transport across membranes) combine the extraction, diffusion, and back extraction of analytes are particularly drawing maximum attention [3].