Ratiometric strategy assisted electrochemical detection of 4-nitrophenol in water samples using nanostructured CuO

Abstract

Copper oxide has been synthesized using the co-precipitation method and employed as a modifier for the electrochemical detection of 4-nitrophenol (4-NP) in water samples. The reason for choosing CuO stems from the presence of two different oxidation states, which has been confirmed through XPS analysis. The ratio between the CuO (Cu¹⁺ to Cu²⁺) oxidation peak and 4-NP oxidation one has been used as the ratiometric signal for the determination of 4-NP. Electrochemical parameters such as the rate constant (k_s) have been calculated using the Laviron equation. The ratiometric approach exhibited a wide linear range (20 μM to 180 μM) four times higher than the routine 4-NP reduction approach. The wide linear range detection for the ratiometric strategy observed might arise from the interaction between CuO and 4-NP. Ex situ (DRS-UV and FT-IR) analysis of CuO/GCE dipped in 4-NP confirms the interaction. The ratiometric strategy for the sensing of 4-NP exhibited a LOD of 118 nM, which is much lower compared to the U.S. Environmental Protection Agency (EPA) MRL limit of 4-NP (430 nM) in drinking water. In addition to this, the ratiometric strategy exhibited better anti-interference ability in the presence of various organic molecules. Finally, the proposed CuO/GCE was applied for the determination of 4-NP in different environmental water samples, and the results were highly satisfactory with recovery values of 95% to 103%. The proposed ratiometric strategy for electrochemical sensing of 4-NP is promising in terms of analytical aspects and can be developed as a commercial electrode for the quantification of 4-NP.