Sol-Gel-Au nano-particle modified carbon paste electrode for potentiometric determination of sub ppb level of Al(iii)

Abstract

This work describes a new carbon paste electrode modified by Sol-Gel-Au nano-particle (SGAN) in the presence of 2,2′-dihydroxy-1-naphthylidine-1′-naphthyl methyl amine (DNMA) as ionophore for determination of Al(III) by potentiometric method. Gold nano-particles (GNPs) were self-assembled onto silica Sol-Gel network and incorporated within carbon paste. The nano-structured matrix with DNMA shows well-defined potentiometric behavior for the determination of Al³⁺ in aqueous solutions. The sensor exhibits significantly enhanced selectivity toward Al³⁺ ions over a wide concentration range of 5.0 × 10⁻¹⁰ to 5.0 × 10⁻² M with a lower detection limit of 2.0 × 10⁻¹⁰ M (0.054 ppb) and a Nernstian slope of 20.0 ± (0.1) mV decade⁻¹ of Al³⁺ activity. It has a fast response time of 5 s and can be used for at least 70 days without any considerable divergence in potentials. The potentiometric response of the electrode is independent of pH of test solution in the pH range 3–7. The interaction between DNMA and Al³⁺ was studied spectrophotometrically and it exhibits that stoichiometry of complex is 1 : 1 in methanol solution. Finally, this electrode was successfully used as an indicator electrode for potentiometric determination of Al³⁺ in some real samples.