Nanoparticle-based materials have played an important role in the development of new electrochemical sensors and received recently tremendous attention for the detection of toxic ions such as nitrate molecules ( \({{\text{NO}}}_{3}^{-}\) and \({{\text{NO}}}_{2}^{-}\) ). Here, we employ La1.7Sr0.3CuO4 (LSCu) and La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) low-cost, highly sensitive nanoparticles modified with black carbon as sensors for the detection of nitrate ions. The modified nanooxides were synthesized by a simple citrate method then prepared with black carbon powder and nafion solution as a sensing matrix on a glassy carbon electrode for the determination of nitrates ions in water using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy as electrochemical techniques. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for structural and morphological characterization. The calculated crystallite size d, using the Debye–Scherrer equation was found to be 325,193 nm for LSCu and 208,317 nm for LSCF by XRD technique. The grain sizes are, respectively, 47.80 nm and 65.05 nm which were extracted by SEM analysis. In this work, the modified sensors based on LSCu and LSCF demonstrate satisfactory response and sensitivities toward nitrate molecules compared with previous works. They characterized with very low detection limits of 0.0014 nM and 0.02 nM, high sensitivities of 58.8 and 57.3 µA.µM−1, respectively, and recorded a wide linear range from 1 M to 10–12 M for LSCF and 4 M to 10–13 M for LSCu.
Both of the modified electrodes demonstrated excellent results in real river water sample with low detection limits of 3.1 nM for LSCu and 3.5 nM for LSCF and very good recoveries of 100.6% and 101.65%, respectively.
