Label-Free Electrochemical Detection of Acetaminophen Using a Gold Nanoparticle–Modified Stainless Steel Electrode

Acetaminophen (AAP), also known as paracetamol, is a widely used ‘over-the-counter’ medicine and one of the leading causes of soil and water contamination worldwide. The improper disposal of pharmaceutical residues during their production and from households poses a serious threat to aquatic systems and the environment. Hence, the development of simple, cost-effective, and reliable methods for AAP detection is of great importance for both health and environmental monitoring. In this work, we report the fabrication and characterization of an inexpensive label-free sensor for AAP detection based on AuNPs electrodeposited onto a stainless steel substrate. The electrochemical response of AAP by the Au-modified electrode exhibited well-defined redox peaks in cyclic voltammetry. Under optimized conditions (pH 5.96 in 0.1 M KH$_{2}$PO$_{4}$), the sensor demonstrated a dual detection behavior: a linear response in the low concentration range (0.8$\mu$M to 0.03 mM) with a sensitivity of 2.08 mA mM$^{-1}$and a sigmoidal response in the higher concentration range (0.03-6.65 mM) with a sensitivity of 0.97 mA mM$^{-1}$. The limit of detection (LOD) in the linear range was calculated to be 0.8$\mu$M. The low-cost fabrication and promising performance of the fabricated sensor highlight its potential for integration into portable devices to monitor AAP contamination in water.