Electroanalytical determination of heavy metals in aqueous solutions by using a carbon paste electrode modified with spent coffee grounds

In this paper, the quantification of Pb2+ and Cd2+ at trace levels was carried out by differential pulse anodic stripping voltammetry technique, using a paste carbon electrode modified with spent coffee grounds (SCG) as working electrode. Different percentages of SCG (40, 50, 60, 70% of SCG) were tested in the experiments; the best electrochemical response was obtained with the electrode modified with 50% of SCG. An experimental design was performed in order to maximize the intensity of the oxidation current, using the accumulation time and the reduction potential as factors. The best experimental conditions for the electrodeposition of the cadmium ions were obtained at an accumulation time of 76 s, and the reduction potential of −1115 mV; while for the electrodeposition of lead ions, the best performance was obtained at an accumulation time of 120 s and a reduction potential of −1200 mV. The detection limit of the carbon paste electrode modified with 50% of SCG were 89 and 90 μM for Cd(II) and Pb(II), respectively, showing the potential of these electrodes as a viable and sustainable alternative for the determination of heavy metals in aqueous solutions. •Spent coffee grounds could be used as a modifying agent of a carbon paste electrode modified (CPEM).•CPEM is an environmentally friendly for the electroanalytical quantification of heavy metals.•The sensitivity of the CPEM is related to the amount of coffee waste inside the electrode.•CPEM with 50% of SCG improves the shape and magnitude of redox peaks of ferrocyanide reaction.•The limits of detection of CPEM are 79 and 80 μM for Pb(II) and Cd(II), respectively.