RESEARCH PAPER Multi-walled carbon nanotubes functionalized with bathocuproinedisulfonic acid: analytical applications for the quantification of Cu(II) Jorge Saldaña 1,2 & Pablo Gallay 1 & Silvia Gutierrez 2 & Marcos Eguílaz 1 & Gustavo Rivas 1 Received: 29 November 2019 /Revised: 27 December 2019 /Accepted: 7 January 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract This work reports the successful non-covalent functionalization of multi-walled carbon nanotubes (MWCNTs) with bathocuproinedisulfonic acid (BCS) and the analytical application of the resulting dispersion (MWCNTs-BCS) to develop an electrochemical sensor for Cu(II) quantification. The sensor was obtained by casting glassy carbon electrodes (GCEs) with MWCNTs-BCS. The sensing mechanism was based on the open circuit preconcentration of Cu(II) at the electrode surface by complexation of Cu(II) through the phenanthroline ring nitrogen of the BCS that supports the MWCNTs, the reduction of the preconcentrated Cu(II), and final differential pulse voltammetry-anodic stripping in 0.020 M acetate buffer, pH 5.00. The sensitivity of the sensor was (2.73 ± 0.08) μA μM -1 , with a linear range between 5.0 × 10 -7 M and 6.0 × 10 -6 M, a detection limit of 0.15 μM (9.5 μgL -1 ), and reproducibility of 6.2% using the same dispersion and 7.1% using three different MWCNTs-BCS dispersions. The quantification of Cu(II) was highly selective even in the presence of As 3+ , Cr 3+ , Cd 2+ , Ni 2+ , Pb 2+ , Co 2+ , Zn 2+ , Fe 2+ , Hg 2+ , Rh, Ir, and Ru. The proposed sensor was successfully used for quantifying Cu(II) in tap water. Keywords Carbon nanotubes . Bathocuproinedisulfonic acid . Copper quantification . Electrochemical sensor Introduction The control of the amount of heavy metals released to the environment has received great attention in the last years mainly due to the better knowledge of their toxic effects to the environment and human health [1, 2]. Among these heavy metals, copper is an essential element that plays a key role in several biological processes [ 3 ]. However, elevated concentration can produce anemia, bone disorders, diarrhea, and neurological disorders [4, 5]. For this reason, the moni- toring of copper level in water is of toxicological and environ- mental concern, and the United States Environmental Protection Agency (USEPA) reported that the concentration of copper should not be higher than 1.30 ppm [6]. Conventional analytical methods for the quantification of heavy metals include atomic absorption spectroscopy, induc- tively coupled plasma/mass spectrometry, inductively coupled mass/atomic emission spectrometry, atomic fluorescence spectrometry, and ultraviolet-visible spectroscopy [7–10]. Even when these techniques are highly sensitive and selective, most of them are time consuming, require expensive instru- ments, and cannot be used as portable devices for on-site detection. In contrast, electrochemical analysis, in particular, stripping-based electrochemical sensors, represent a powerful and effective tool for the detection of heavy metals [11, 12]. The use of a suitable ligand associated with stripping volt- ammetry has allowed the fast, selective, and quantitative for- mation of metal-ligand complex at the electrode surfaces [13]. Several ligands have been used to modify different electrodes for the electrochemical determination of copper such as L- Published in the topical collection Euroanalysis XX with guest editor Sibel A. Ozkan. * Silvia Gutierrez gutigs59@hotmail.com * Marcos Eguílaz marcos.eguilaz@hotmail.com * Gustavo Rivas grivas@fcq.unc.edu.ar 1 INFIQC, Departamento de Físicoquimica, Facultad de Ciencias Químicas, Ciudad Universitaria, 5000 Córdoba, Argentina 2 Departamento de Química, Universidad de Guanajuato, 36040 Guanajuato, Mexico Analytical and Bioanalytical Chemistry https://doi.org/10.1007/s00216-020-02396-z