Dual-monomer molecularly imprinted polymer sensor for paracetamol voltammetric determination

Paracetamol is an emerging pharmaceutical contaminant widely detected in aquatic environments because of its large-scale consumption and persistence through conventional wastewater treatment processes. Even at trace levels, its continuous input into water bodies raises environmental concern and demands sensitive and selective analytical approaches for reliable monitoring. In this work, a screen-printed electrode (SPE) modified with a molecularly imprinted polymer (MIP) was developed for PAR quantification. The carbon-based SPEs were produced in the laboratory from a conductive ink composed of graphite powder, nanographite (surface-enhanced flake graphite), and alkyd resin. Functional monomers were selected based on molecular modeling using quantum mechanics calculations. The MIP film was prepared by direct electropolymerization on the SPE, using chronoamperometry from a solution containing caffeic acid and L-methionine as monomers, and PAR as the template molecule. A non-imprinted polymer (NIP) film was obtained following the same methodology, but in the absence of PAR. The sensors were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Under optimized conditions, calibration curves for PAR were obtained using unmodified SPE, NIP sensor, and MIP sensor, with detection limits of 4.4 × 10 – 6 , 2.7 × 10 – 6 , and 5.0 × 10 – 8 mol L – 1 , respectively. The MIP sensor showed adequate selectivity, and good reproducibility (RSD = 6.3%), stability (85 days) and reusability (up to 7 measurements, with recalibration) or use for a single analysis (disposable). The MIP sensor was successfully applied in the analysis of PAR in aqueous matrices, with relative error below 10%.