Comparative studies on carbon paste electrodes based on three dithiocarbamate podands as ionophore in Ag(i) sensors

Abstract

Three dithiocarbamate podands, [N,N′(bis[(1-oxoethyl) morpholine-2-carbodithioate])-2,6- diaminopyridine] (P₁), [N,N′(bis [(1-oxoethyl)piperidine-2-carbodithioate])-2,6-diaminopyridine] (P₂) and [N,N′(bis[(1-oxoethyl)diethylamine-2-carbodithioate])-2,6-diaminopyridine] (P₃) have been synthesized and used as ionophores for Ag⁺-selective carbon paste electrodes. The construction, response characteristic and application of the silver ISEs are investigated. Potentiometric responses reveal that the flexibility of the ligands has a great effect on the selectivity and sensitivity toward Ag⁺ ions. Among the podands, the best performance was achieved with the sensor using P₁ as ionophore. The proposed sensor exhibits Nernstian response with the slope of 58.6 ± 0.6 mV/decade in the concentration range of 8.2 × 10⁻⁸–1.5 × 10⁻² mol L⁻¹ of Ag⁺ and a lower detection limit of 6.3 × 10⁻⁸ mol L⁻¹. The linear concentration range of the electrodes modified with P₂ and P₃ were also 2.5 × 10⁻⁶–1.2 × 10⁻² and 6.3 × 10⁻⁷–1.2 × 10⁻² mol L⁻¹, respectively. The response time of the electrode based on p₁ was 8 s and its potential was independent of pH in the range of 2.9–8.2. The electrodes were highly selective to Ag⁺ ions over a large number of mono, bi, and tri-valent cations which make them unique in the analysis of real samples.