Effortless lab-manufactured carbon and alumina-based composite sensors for enzymeless sensitive amperometric detection of dopamine in clinical and environmental samples

Developing new sensors presenting low-cost, portability, and disposability features is of paramount in the electrochemical field. Thus, this work proposes the fabrication of lab-made composite electrodes using acrylonitrile butadiene styrene, graphite, and aluminum oxide. In this investigation, the amount of aluminum oxide (0 to 12.25 w/w) was carefully optimized, and its impact on the electrochemical performance of the electrode was observed using the ferri-ferro redox probe and dopamine (DOP) as a proof of concept. This innovative electrode was characterized by spectroscopy, morphological, elemental, and electrochemical techniques. Using the alumina-loaded electrode, significantly improved cyclic voltammetric responses regarding peak currents and peak-to-peak separation were obtained for both evaluated species. This sensor was integrated into the batch injection analysis system for amperometric monitoring of DOP in synthetic biological fluids (saliva and urine) and tap water. The developed method showed a wide linear range (10 to 1000 µmol L⁻¹), a low detection limit (2.6 µmol L⁻¹), and a high analytical frequency (182 analyses per hour). Furthermore, it was precise (RSD < 5%), accurate (recoveries between 90.5 and 107.3%), and selective. Therefore, it can be considered a low-cost alternative analytical tool for electrochemical sensing of DOP in samples of clinical and environmental interest.