Plasma-Activated 3D-Printed Electrode for the Determination of Tolfenamic Acid in Environmental Samples

Abstract The occurrence of tolfenamic acid (TA) in aquatic environments has raised concerns regarding its potential environmental impacts, highlighting the need for rapid, sensitive, and low-cost analytical methods for its determination. In this work, a conductive CB/PLA filament was fabricated through a solvent-free thermal mixing approach and used to produce a 3D-printed electrochemical sensor for TA determination. This strategy provides a greener and scalable route for electrode fabrication. Atmospheric air plasma treatment was applied to improve the electrochemical performance of the CB/PLA electrode. SEM images revealed the partial removal of the insulating PLA matrix, increasing the exposure of the conductive carbon sites. This modification resulted in lower charge-transfer resistance (Rct from 33.4 to 7.6 kΩ). Under optimized differential pulse voltammetry conditions, the plasma-treated electrode (CB/PLA-PT) exhibited a linear response toward TA in the concentration range of 1.91–20.1 μmol L–1, with detection and quantification limits of 0.54 and 1.80 μmol L–1, respectively. The sensor demonstrated satisfactory precision (RSD ≤ 5.7%) and selectivity in the presence of common interfering species. Its applicability was successfully demonstrated in spiked river and tap water samples, yielding recovery values between 92 and 105%. The proposed approach combines 3D printing and reagent-free plasma activation to provide a simple and environmentally friendly platform for the electrochemical determination of TA in environmental waters.