ORIGINAL ARTICLE A new nano-composite electrode as a copper (II) selective potentiometric sensor Abbas Afkhami • Hosein Khoshsafar • Tayyebeh Madrakian • Ali Shirzadmehr Received: 16 September 2013 / Accepted: 31 December 2013 Ó Iranian Chemical Society 2014 Abstract 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 Cu 2? nano-composite potentiometric carbon paste sensor containing multi-walled carbon nanotubes (MWCNTs), nanosilica particles, and room temperature ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoro- methylsulfonyl)imide, [BMP]Tf 2 N). This potentiometric sensor responds to copper ions in a wide linear dynamic range of 4.50 9 10 -8 to 1.00 9 10 -2 mol L -1 with Nernstian slope of 29.64 ± 0.10 mV per decade. The detection limit of 2.34 9 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 Cu 2? ions in the presence of a large number of alkali, alkaline earth, transition and heavy metal ions. This sensor was success- fully applied in the determination of copper ions in water and waste water samples. Keywords Potentiometric carbon paste sensor  Copper  Multi-walled carbon nanotubes  Nanosilica particles  Ionic liquids Introduction Heavy metal ions are widespread contaminants of great environmental concern as they are non-degradable and thus persistent [1]. It is well perceived that there is a permissible limit for each metal, above which it is generally toxic [2, 3] and some are even hazardous. Industrial wastes containing metal ions such as nickel, lead, copper, zinc and aluminum are common because their metals are used in a large number of industries such as electroplating, battery man- ufacture, mine, metal finishing, brewery, and pharmaceu- ticals and so on [4–7]. Although copper is an essential element in the human body and plays an important role in various biological processes, yet large amounts of Cu 2? ions can be tolerated by human beings; however, excessive dosage and long-term exposure may cause irritation of the nose, mouth and eyes, and it causes headache, stomach ache, dizziness, vomiting and diarrhea [5–10]. Therefore, it is desirable to develop simple, selective, efficient and eco- friendly methods for the determination of Cu 2? in envi- ronmental and biological samples. In recent years, different instrumental techniques, including atomic absorption spectrometry [11], spectrophotometry [12], phosphores- cence quenching method [13], and chemiluminescence [14] have been reported in the determination of copper. How- ever, these instrumental techniques are too expensive and are not available in most analytical laboratories or need time consuming procedures. Thus, the development of convenient and direct methods for the assay of copper ions in different samples is an urgent need. Electrochemical sensors have been widely used to detect various substances due to their high sensitivity and desirable selectivity in their responses [15–21]. Potentiometric sensors based on carbon paste electrodes (CPEs) offer several advantages such as ease of preparation, simple instrumentation, fast A. Afkhami (&)  H. Khoshsafar  T. Madrakian  A. Shirzadmehr Faculty of Chemistry, Bu-Ali Sina University, Hamedan, Iran e-mail: afkhami@basu.ac.ir 123 J IRAN CHEM SOC DOI 10.1007/s13738-014-0406-x