A graphite paste electrode modified with 3% Agnéby clay was developed for the sensitive electrochemical detection of perfluorooctanoic acid (PFOA). The natural clay was purified and characterized by X-ray diffraction prior to its incorporation into the electrode matrix. The interaction between Agnéby clay and PFOA plays a key role in enhancing the electrochemical response through adsorption and preconcentration effects, leading to increased active surface area and improved electron transfer kinetics.

Electrochemical measurements performed using cyclic voltammetry and square wave voltammetry revealed significantly enhanced oxidation signals compared to the unmodified electrode. The modified electrode exhibited a detection limit of 0.49×10⁻⁶ mol⋅L⁻¹, along with good stability and reproducibility.

These results demonstrate that Agnéby clay is an effective, low-cost modifier for the development of high-performance electrochemical sensors, offering promising applications for environmental monitoring of perfluorinated compounds.