Lowering detection limits of copper(II)-selective carbon paste electrodes using an SNO- and an SNNS- Schiff base ligands

Interestingly, this work presents two newly designed copper(II)-selective carbon paste electrodes with distinctively low detection limits which is attained utilizing the Schiff base ligands 2-(2-hydroxyphenylimino)carboxythiophene (L1) and 1,2-di(2-carboxythiopheneimino] benzene (L2). The sensors exhibit a Nernstian slope of 29.10 and 29.28 mVdecade⁻¹ for Cu(II) ion over a wide concentration range from 1.18 ​× ​10⁻⁷ – 1.00 ​× ​10⁻² ​M and 7.91 ​× ​10⁻⁸ – 1.00 ​× ​10⁻² ​M with the detection limits of 1.00 ​× ​10⁻⁷ ​M and 5.28 ​× ​10⁻⁸ ​M for L1 and L2 respectively. These sensors exhibit short response time (about 2 ​s) and good stability over the pH range 2.5–5.8. In addition, the present sensors show fairly good selectivity toward copper(II) ion in comparison to other common cations. Furthermore, they were satisfactorily used as indicator electrodes in complexometric titration with EDTA and for determination of copper(II) in water, tea and urine samples.