Development of a Dy₂O₃@Eu₂O₃-carbon nanofiber based electrode for highly sensitive detection of papaverine

A sensitive electrochemical method based on carbon nanofibers (CNFs) and bimetallic nanoparticles of dysprosium oxide (Dy₂O₃) and europium oxide (Eu₂O₃) was developed for the determination of papaverine in pharmaceuticals and human urine. Several electrodes were compared in respect to their electrochemically active surface area calculated as 0.0603, 0.1300, 0.3440, 0.3740 and 0.4990 cm² for bare GCE, CNFs/GCE, Eu₂O₃-CNFs/GCE, Dy₂O₃-CNFs/GCE and Dy₂O₃@Eu₂O₃-CNFs/GCE, respectively. Electrodes were also compared in respect to their performance towards the voltammetric process of papaverine. The peak potential (Epa) of papaverine was 1.094 V, 0.993 V, 0.978 V, 0.969 V and 0.966 V at unmodified GCE, CNFs/GCE, Eu₂O₃-CNFs/GCE, Dy₂O₃-CNFs/GCE and Dy₂O₃@Eu₂O₃-CNFs/GCE, respectively. This indicated that the oxidation peak potential of papaverine shifted gradually towards the negative potentials and the peak current increased gradually from unmodified GCE to CNFs/GCE, Eu₂O₃-CNFs/GCE, Dy₂O₃-CNFs/GCE and Dy₂O₃@Eu₂O₃-CNFs/GCE. The influence of experimental parameters such as scan rate and pH on the voltammetry of papaverine was studied. The Dy₂O₃@Eu₂O₃-CNFs/GCE system presented a dynamic working range between 1.0 × 10^-7 and 2.0 × 10^-6 M with a detection limit of 1.0 × 10^-8 M for papaverine. The platform (Dy₂O₃@Eu₂O₃-CNFs/GCE) exhibited excellent sensitivity and selectivity for papaverine in the presence of uric acid and was successfully applied for determining papaverine in pharmaceuticals and urine samples.