Sensitive Voltammetric Determination of Phenylethylamine in Dark Chocolate via a Carbon Nanofibers–Dysprosium Oxide Nanocomposite

Abstract

A sensitive voltammetric sensor was developed to selectively determine phenylethylamine (PEA), a naturally occurring biogenic amine, in dark chocolate and biological fluids. The sensor was fabricated by modifiying a glassy carbon electrode (GCE) with carbon nanofibers (CNFs) and dysprosium oxide (Dy₂O₃) nanoparticles. The Dy₂O₃ nanoparticles were prepared by precipitation using ammonia, followed by calcination at 500 °C for 6 h. PEA showed a reversible electrochemical response, with oxidation and reduction peaks at 0.099 and 0.071 V, respectively, and a peak-to-peak separation of 28 mV. The GCE/CNFs@Dy₂O₃ electrode had a higher electroactive surface area (0.366 cm²) than bare GCE (0.054 cm²) and GCE/CNFs (0.197 cm²). It also showed a lower charge-transfer resistance of 123 Ω, compared with 800 and 450 Ω for the two respective electrodes. Under optimized conditions, the sensor showed a linear response to PEA over the range of 2.0 × 10⁻⁸–1.8 × 10⁻⁵ M, with a detection limit of 1.4 × 10⁻⁹ M. PEA concentrations measured in three commercial dark chocolate samples were 66.7 ± 1.3, 69.5 ± 1.4, and 58.3 ± 1.3 µg g⁻¹. The sensor also showed good repeatability and reproducibility, with satisfactory recovery results, indicating that it can be used for the determination of PEA in food and biological samples.