Desenvolvimento de sensores eletroquímicos impressos em papel do tipo reagent˗free modificados com polianilina para a determinação de paracetamol em amostras ambientais e biológicas.

Abstract

Paracetamol, also known as acetaminophen (AC), is a drug widely used as an analgesic and antipyretic, making its detection important for pharmaceutical quality control and environmental monitoring. This work proposes the development of an electrochemical platform based on reagent-free screen-printed paper electrodes modified with polyaniline. This process was performed by cyclic voltammetry - CV from (-0.2 to 1.2 V vs. graphite pseudo-reference), using 0.0075 mol L−1 of the aniline monomer. The formation of the polymeric film on the working electrode (referred to as PAni/SPE), was achieved after 40 cycles, improving electron transfer and increasing the electroactive surface area from 3.55 to 6.98 mm², accompanied by an increase in the real area from 125.7 to 256.9%. The electrochemical characterization of the PAni/SPE platform was performed by CV, from (-0.8 to 0.8 V vs. graphite pseudo-reference), in 1.0 mol L−1 [Fe(CN)₆]³⁻/⁴⁻ in 0.1 mol L−1 KCl. The morphology and hydrophobicity evaluation of the platforms were assessed by scanning electron microscopy (MEV) and contact angle measurements, respectively. AC detection was performed by differential pulse voltammetry (DPV), using a 0.1 mol L−1 PBS solution at pH 7.0 as the electrolyte. A pH optimization study was carried out for the detection of 2 × 10−4 mol L−1 AC in 0.1 mol L−1 PBS, within the pH range of 6.0 to 9.5, with pH 7.0 being the optimal value for detection. AC was studied over a concentration range from 1.0 to 100 μmol L−1, yielding two linear ranges with different R² values (0.997 and 0.993) and achieving limits of detection (LOD) and quantification (LOQ) of 0.026 μmol L−1 and 0.0853 μmol L−1, respectively. The interference study demonstrated that, although compounds such as caffeine, diclofenac, ibuprofen, losartan, and progesterone caused variations in the peak current, the platform maintained a selective response toward AC. In addition, recovery assays in lake water, tap water, and synthetic urine samples presented values between 75.28% and 99.8%, with a relative standard deviation lower than 2.51%, demonstrating the applicability of the sensor in complex samples. Thus, the results demonstrate that the PAni/SPE platform is a promising, portable, sensitive, low-cost, and environmentally friendly alternative for the electrochemical determination of paracetamol.