3D-printed carbon black/polylactic acid electrode modified with silver particles: a powerful alternative and cost-effective sensor for nitrate sensing in real water samples

Monitoring nitrate in aquatic systems is of fundamental importance since its presence at high levels can result in adverse effects on human health. Thus, in this work, manufactured carbon black (CB)/polylactic acid (PLA)-based 3D-printed electrochemical sensors modified with electrodeposited silver particles (AgPs) for nitrate analysis in real water samples. Raman and FT-IR spectra, scanning electron microscopy images, and analysis by energy-dispersive spectroscopy confirmed the presence of AgPs on the porous carbonaceous surface. The preliminary electrochemical studies showed that using the modified electrode (CB-PLA/AgPs) an incredible increase in the electrochemical response (around 16.5-fold in terms of current density) was obtained for the electroreduction of nitrate at around - 1.08 V vs. Ag|AgCl|KCl(sat.) compared to the unmodified electrode (CB-PLA). The linear sweep voltammetry technique was employed whose instrumental parameters have been carefully optimized. Under optimized conditions, a linear range between 5 and 80 mg L-1 (R-2 > 0.99) was achieved, with a detection limit of 2.7 mg L-1, which is below the maximum level permitted (50 mg L-1) by the World Health Organization (WHO). Repeatability (intra-electrode, n = 8) and reproducibility (inter-electrode, n = 3) studies were performed, and RSDs < 2.1% were found, demonstrating good precision of the analysis and reproducible manufacturing process of the sensors. Moreover, the proposed sensor proved to be selective in the presence of other inorganic compounds frequently found in environmental waters. Importantly, in the recovery tests, percentage values between 91 and 117% confirmed the accuracy and reliability of the analyses. Thus, the developed strategy can be useful for nitrate sensing in real water samples in remote locations.