RESEARCH PAPER Cu 2+ ion-sensitive surface on graphite electrodes Ignacio Pedre 1 & Lucila Paula Méndez De Leo 1 & Graciela Alicia González 1 Received: 18 June 2019 /Revised: 27 August 2019 /Accepted: 4 September 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract A new electrochemical interface based on polyacrylic acid (PAAcid) immobilized in a Nafion® polymeric matrix on graphite screen-printed electrodes for detecting copper is presented. The copper is retained in the surface due to the capacity of the polyacid to chelate metals, and quantified using square wave voltammetry. The response was characterized by spectroscopic techniques (UV-vis-IR), which confirmed the chelation from the Cu 2+ ions by the acid. A calibration curve is presented, showing good linearity and repeatability and its usefulness as a sensor. The range of operation goes from 15 to 50 μM, with a detection limit of 12 μM, making the sensor useful for measurements in environmental samples (after a preconcentration step) and in drinking water. Keywords Copper . Sensitive interface . Environmental electroanalysis . FT-IR characterization Introduction Heavy metals represent a serious threat for natural water sys- tems, because they are persistent and can be accumulated in living organisms, and therefore biomagnified in the upper levels of the food web. For these reasons, increased attention is paid to their detection and removal from contaminated wa- ter and wastewater, and their permissible upper limits in water and food decrease each year [1]. Metals and metalloids such as Cu, Cd, Al, Cr, Zn, Fe, Hg, As, and Pb are often released in large quantities during or after the mining activity and can lead to the pollution of aquatic ecosystems. Conventional analytical methods for the determination of metals at low concentrations include the use of techniques such as atomic spectroscopies (atomic absorption spectroscopy, in- duced coupled plasma), ultraviolet-visible spectroscopy, ion chromatography, capillary electrophoresis, and X-ray fluores- cence spectroscopy. Although these analytical methods show excellent figures of merit in terms of selectivity and sensitivity, their major disadvantages are the tedious sample preparation and the use of expensive instrumentation. On the other hand, these determinations cannot be performed on the field. Therefore, an accurate, fast, miniaturized, inexpensive, and sen- sitive means of monitoring metals in environmental samples and drinking water is highly desirable [2]. The method should be simple so that it can be easily operated by a layman. In particular, copper is an important element for the indus- try (electroplating, printed circuits, fertilizers, etc. [3]), and although it is essential for the living organisms and the envi- ronment, it becomes dangerous when present in high concen- trations [2]. For example, in humans, an excessive ingestion of Cu 2+ may cause serious health problems such as Wilson, Menkes, and Alzheimer’s diseases, and for that reason, its permissible concentration level in drinking water has been regulated by the US EPA as 1.3 mg/L (20 μM) [4]. Copper is also considered a water pollutant, which can reach water bodies through natural processes and anthropogenic activities such as mining and petroleum refining [5]. Although copper concentrations in environmental samples vary greatly depending on the source, the location, and the sampling method, we include some values as a guide: as men- tioned before, the permissible limit in drinking water is 20 μM. On the other hand, according to [6], concentrations of copper in natural waters range from 17 to 24 nM in rivers, 5 to 20 nM in lakes, 0.5 to 5 nM in the Pacific Ocean, and from 10 to 300 nM in rain water. Other sources [7] estimated a world average concentration of copper in rivers to be * Ignacio Pedre ipedre@qi.fcen.uba.ar * Graciela Alicia González graciela@qi.fcen.uba.ar 1 INQUIMAE – Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Universitaria, Pabellón 2, 1428 Buenos Aires, Argentina Analytical and Bioanalytical Chemistry https://doi.org/10.1007/s00216-019-02142-0