A macrocyclic ligand ‘‘7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cycloocta- decane-6,14-dione’’ as an efficient ionophore was used into a new Cu2+ nano-composite potentiometric carbon paste sensor containing multi-walled carbon nanotubes (MWCNTs), nanosilica particles, and room temperature ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP]Tf 2 N). This potentiometric sensor responds to copper ions in a wide linear dynamic range of 4.50 * 10-8 to 1.00 * 10-2 mol L-1 with Nernstian slope of 29.64 ± 0.10 mV per decade. The detection limit of 2.34 * 10-8 mol L-1 was obtained at the pH range 3.5–6.0. It has a fast response with response time of about 10 s, and can be used for at least 16 weeks without any considerable divergence in the potentials. The suggested sensor thus allows sensitive, selective, simple, low cost, and stable electrochemical sensing of Cu2+ ions in the presence of a large number of alkali, alkaline earth, transition and heavy metal ions. This sensor was successfully applied in the determination of copper ions in water and waste water samples.
