Nitrate (NO3−) contamination is becoming a major concern due to the negative effects of an excessive NO3−
presence in water which can have detrimental effects on human health. Sensitive, real-time, low-cost, and portable measurement
systems able to detect extremely low concentrations of NO3− in water are thus becoming extremely important. In this work, we
present a novel method to realize a low-cost and easy to fabricate amperometric sensor capable of detecting small concentrations of
NO3− in real water samples. The novel fabrication technique combines printing of a silver (Ag) working electrode with subsequent
modification of the electrode with electrodeposited copper (Cu) nanoclusters. The process was tuned in order to reach optimized
sensor response, with a high catalytic activity toward electroreduction of NO3− (sensitivity: 19.578 μA/mM), as well as a low limit of
detection (LOD: 0.207 nM or 0.012 μg/L) and a good dynamic linear concentration range (0.05 to 5 mM or 31 to 310 mg/L). The
sensors were tested against possible interference analytes (NO2−, Cl−, SO42−, HCO3
−, CH3COO−, Fe2+, Fe3+, Mn2+, Na+, and Cu2+)
yielding only negligible effects [maximum standard deviation (SD) was 3.9 μA]. The proposed sensors were also used to detect
NO3− in real samples, including tap and river water, through the standard addition method, and the results were compared with the
outcomes of high-performance liquid chromatography (HPLC). Temperature stability (maximum SD 3.09 μA), stability over time
(maximum SD 3.69 μA), reproducibility (maximum SD 3.20 μA), and repeatability (maximum two-time useable) of this sensor were
also investigated