Nitrate (NO
3
–
) contamination is becoming
a major concern due to the negative effects of an excessive NO
3
–
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
NO
3
–
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 NO
3
–
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 NO
3
–
(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 (NO
2
–
,
Cl
–
, SO
4
2–
, HCO
3
–
, CH
3
COO
–
, Fe
2+
, Fe
3+
,
Mn
2+
, Na
+
, and Cu
2+
) yielding only
negligible effects [maximum standard deviation (SD) was 3.9 μA].
The proposed sensors were also used to detect NO
3
–
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.