Lead-selective poly(vinyl chloride) membrane electrodes based on acyclic dibenzopolyether diamides

Abstract

Lipophilic acyclic dibenzopolyether diamides, 12 kinds, have been designed to prepare solvent polymeric membrane ion-selective electrodes (ISEs) for Pb 2+. The ionophores include 1,5-bis[2-( N, N-dialkylcarbamoylmethoxy)phenoxy]-3-oxapentanes 1–4, 1,5-bis[2-( N, N-dialkylcarbamoylpentadecyloxy)phenoxy]-3-oxapentanes 5–8, and 1,2-bis[2-(2′- N, N-dialkylcarbamoylpentadecyloxy)phenoxy]ethanes 9–12. Linear response concentration range of the ISE based on 9 is 3 × 10 −2 – 1 × 10 −6 M of Pb 2+ (average slope = 28.5 mV decade −1). Potentiometric selectivities of the ISEs based on 1–12 for Pb 2+ over other heavy metal cations, alkali metal cations, and alkaline earth metal cations have been assessed. These ISEs exhibit remarkably high selectivities for Pb 2+ relative to heavy metal cations, such as Cu 2+, Fe 2+, and Ni 2+, the selectivity coefficients ( K Pot Pb,Cu) being 5 × 10 −5 − 6 × 10 −5 for 1–4 and ca. 6 × 10 −4 for 9. For the Pb 2+ selectivities over alkali metal cations, such as Na + and K +, 9 which has an ethylene glycol spacer and a N, N-diethyl group is superior to other dibenzopolyether diamide ionophores 1–8 and 10–12.