Potentiometric determination of nanomolar concentration of Cu (II) using a carbon paste electrode modified by a self-assembled mercapto compound on gold nanoparticles

A mercapto compound of bis [o-(N-methylidenamino-2-thiol-1,3,4-thiadiazole-5-yl) phenoxy] ethane (BMTTE) self-assembled on gold nanoparticles, was used as modifier to construct a chemically modified carbon paste electrode. The prepared electrode exhibit a Nernstian slope of 29.3 ± 0.2 mV/decade towards Cu (II) ion over a wide concentration range of 4.0 × 10−9 to 2.2 × 10−3 mol L−1. The limit of detection of the electrode was found 1.6 × 10−9 mol L−1. The potentiometric response of the electrode based on BMTTE is independent of pH of test solution in the pH range of 4.0-9.0 with a response time of 15 s. The proposed sensor shows fairly good discriminating ability towards Cu2+ ion in comparison with many hard and soft metal ions. Finally, the proposed electrode was successfully used as an indicator electrode in potentiometric titration of copper ion with EDTA and in direct determination of copper (II) ion in some water samples.