Analytical Sciences

A Coated Wire-type Lead(II) Ion-Selective Electrode Based on a Phosphorylated Calix[4]arene Derivative

Mohammad Reza YAFTIAN,* Saeed RAYATI,* Daryoush EMADI,* and Dominique MATT**

*Department of Chemistry, Faculty of Science, Zanjan University, P. O. Box 45195-313 Zanjan, Iran
**Laboratoire de Chimie Inorganique Moléculaire, Université Louis Pasteur, UMR 7513 CNRS, 1 Rue Blaise Pascal, F-67008 Strasbourg, France

The preparation of a lead-selective electrode based on 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(diphenylphosphinoylmethoxy)calix[4]arene (1) as an ionophore is reported. The plasticized PVC membrane containing 30% PVC, 57% ortho-nitrophenyloctylether (NPOE), 4% sodium tetraphenylborate (NaTPB) and 9% ionophore 1 was directly coated on a graphite electrode. It exhibits a nearly Nernstian slope of 28.0 ± 0.2 mV decade^-1 over a concentration range of 1 × 10^-5 - 1 × 10^-2 mol dm^-3 with a detection limit of 1.4 × 10^-6 mol dm^-3. The response time of the electrode was found to be ca. 17 s. The potential of the sensor was independent of the pH variation in the range 3.5 - 5.0. The selectivity of the electrode performance towards lead ions over Th⁴⁺, La³⁺, Sm³⁺, Dy³⁺, Y³⁺, Ca²⁺, Sr²⁺, Cd²⁺, Mn²⁺, Zn²⁺, Ni²⁺, Co²⁺, NH₄⁺ Ag⁺, Li⁺, Na⁺ and K⁺ ions was investigated. The prepared electrode was used successfully as an indicator electrode for a potentiometric titration of a lead solution using a standard solution of EDTA. The applicability of the sensor for Pb²⁺ measurements in various synthetic water samples spiked with lead nitrate was also checked.

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