Hydrazine-functionalized zeolite electrochemical sensor for trace-level monitoring of carboxin in environmental samples

Oliveira P.C.; Lima G.A.O.; Jeller A.H.; Santos J.S.; Pontes M.S.; da Silva J.L.; Santiago E.F.; Arruda G.J. · Electrochimica Acta (2026) · DOI: 10.1016/j.electacta.2026.148929

Resumen

This work reports a new simple, inexpensive, rapid, sensitive, and selective electrochemical sensor for the fungicide carboxin based on a glassy carbon paste electrode modified with hydrazine-functionalized zeolite. Electrochemical characterization was performed using cyclic voltammetry, square wave voltammetry, electrochemical impedance spectroscopy, and morphological characterization by scanning electron microscopy. The electrochemical variables investigated were the electroactive area of the electrode, the number of electrons, the electron transfer coefficient, the standard rate constant of the electrode surface reaction, the surface coverage, and the double-layer capacitance, with a proposal for the electrochemical oxidation mechanism of carboxin on the electrode surface. The electrode obtained from the functionalization of zeolite with hydrazine increased the peak current by 6 times compared to the unmodified electrode, and by 19 times when electrochemical deposition was used. This modification of the zeolite with hydrazine caused an increase in the double-layer capacitance, a decrease in the electron transfer coefficient, and a 91-fold increase in the standard rate constant of the reaction. The developed method using square wave voltammetry and the modified voltammetric sensor, under optimal conditions, showed a linear range for carboxin from 0.48 to 15.80 μmol L⁻¹, a detection limit of 34.61 nmol L⁻¹, and a quantification limit of 115.37 nmol L⁻¹. The proposed method was used to quantify carboxin in tap water and lake water. The obtained recovery rates were between 98% and 103% with a relative standard deviation (RSD) <8%, demonstrating its suitability for reliable monitoring of carboxin in environmental waters.

Instituciones: Universidad Peruana Cayetano Heredia