Environment pollution, particularly by metals, is a serious problem confronting society today, because some metals are toxic even at low concentrations (Galaris & Evangelou, 2002). Copper is one of the most used metals, mainly in

electrical industries, galvanisation, fertilizers, mining activities, smelting and refining of metals, and is present in pigments, pesticides and fungicides. Since it is a widely employed element, it has a high potential for contamination and may be present in different types of samples including water and sediments from rivers and lakes, beverages, and food (Ngah, Endud, & Mayanar, 2002). Due to its technological importance, many sensors have been developed for copper determination, such as ion-selective learn more electrodes (Gismera, Hueso, Procopio, & Sevilla, 2004), self-assembled monolayer modified gold electrodes (Mohadesi Pictilisib price & Taher, 2007), bismuth film electrodes (Pacheco et al., 2008) and modified carbon paste electrodes (MCPE) (Cesarino, Marino, Matos, & Cavalheiro, 2008). The use of these sensors with voltammetric and chronoamperometric techniques shows some advantages, such as high sensitivity and precision and low cost of the equipment, when compared to spectroscopic techniques, for instance, graphite furnace atomic adsorption spectroscopy and inductively coupled plasma mass spectroscopy

(Mhammedi, Achak, & Chtaini, 2009). The application of MCPE in metal analysis by stripping voltammetry has attracted considerable attention, mainly because the introduction of a chemical modifier allows the concentration of metallic ions at the electrode surface, either by complexation or electrostatic attraction, which of leads to more sensitive electroanalytical procedures with lower

detection limit values (Takeuchi, Santos, Padilha, & Stradiotto, 2007). Different chemical modifiers have been used in the construction of carbon paste electrodes, such as aminopropyl-grafted silica gel (Etienne, Bessiere, & Walcarius, 2001), 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyrimidine thione ( Abbaspour & Moosavi, 2002), carbamoylphosphonic acid self-assembled monolayer on mesoporous silica ( Yantasee, Lin, Fryxell, & Busche, 2004), natural zeolite ( Alpat, Yuksel, & Akcay, 2005), and 2-aminothiazole organofunctionalized silica ( Takeuchi et al., 2007). These electrodes show several advantages including easy fabrication and rapid renewal, low background current, low cost, no toxicity, stability in various solvents and a wide electrochemical window ( Estévez-Hernández, Naranjo-Rodriguez, Hidalgo-Hidalgo de Cisneros, & Reguera, 2007). Moreover, the use of these electrodes combined with electroanalytical techniques, such as stripping voltammetry, allows different experimental conditions to be set, enhancing the electrode performance.