Detection of copper ion in sugarcane spirit using polydimethylsiloxane functionalized with 2-aminothiazole-modified carbon paste electrode

Copper ions were detected in sugarcane spirit using an aminothiazole-functionalized polydimethylsiloxane conductive polymeric network, as a modifier for a carbon paste electrode. This polymeric network of polydimethylsiloxane (PDMS) containing graphite functionalized with 2-aminothiazole (AMTZ) was prepared through a two-stage synthesis. In the first stage was prepared a conductive matrix consisting in a PDMS network with the carbon dispersed, using as crosslinker the silane 3-chloropropyltrimethoxysilane (CPTMS). In the second stage, the chlorine attached to the PDMS network was exchanged for the 2-aminothiazole, generating a functional PDMS conductive network able to interact with metals in solution. The PDMS-conductive network was prepared with different amounts of AMTZ, according to PDMS-to-3-chloropropyltrimethoxysilane ratios (1.00:0.25, 1.00:0.50, and 1.00:0.90 m/m) obtained in the first stage, generating the electrodes A25, A50 and A90. The PDMS-conductive networks were characterized via thermogravimetric analysis and attenuated total reflectance Fourier-transform infrared spectroscopy. The conductive properties of the prepared electrodes were studied via cyclic voltammetry using [Fe(CN) 6 ] 3−/4− . The electrode A25 presented a peak separation of 0.113 V, anodic/cathodic current ratio of 0.69, and the highest current density (400 µA cm −2 ). The total impedance values calculated by electrochemical impedance spectroscopy for A90, A50, and A25 were 478.63, 354.80, and 35.48 kΩ, respectively. The electrode A25 showed a high capacitive character and a low total impedance. The simulated equivalent circuit shows that the electrode A25 presented the lower resistance. The electrochemical behavior of the electrodes described above with the Cu ion in an aqueous medium was studied using square-wave voltammetry. The electrode A25 showed high current densities (200.00 μA cm −2 ), probably because of its high amount of AMTZ. Using anodic stripping voltammetry with working dynamic range of 2.00–19.60 µmol L −1 was performed the determination of Cu ion in an aqueous medium and sugarcane spirit with a detection and quantification limits of 0.12 and 0.40 µmol L −1 , respectively. The values obtained for detection of Cu ion were compared with the standard method for Cu determination, atomic absorption spectroscopy, with a relative error of 0.15 for sugarcane spirit sample. The electrode A25 presented potential to be applied as electrochemical sensor for detecting copper ions. Graphical abstract