Simultaneous Detection of Epicatechin and Theophylline in Black Tea with Nano Cupric Oxide Infused Graphite Electrode

A novel cupric oxide nanoparticles (CuO NPs) infused graphite electrode (CuO@GP) was synthesized for simultaneous detection of epicatechin (EC) and theophylline (TH) in black tea. The CuO NPs were synthesized via the sol–gel method and characterized using X-ray diffraction and a scanning electron microscope. The electrochemical sensor performance was studied using cyclic voltammetry and differential pulse voltammetry revealing the presence of TH and EC simultaneously in black tea. The electrode demonstrated a linear range of 50.0–100.0 [Formula: see text]M for both analytes, with a room temperature limit of detection (4.0 [Formula: see text]M for EC, 27.0 [Formula: see text]M for TH). Under the optimal conditions, it showed repeatability (with a relative standard deviation (RSD): 1.61% EC, 0.96% TH), reproducibility (RSD: 1.07% EC, 1.14% TH) and stability (RSD: 2.16% EC, 2.15% TH). CuO@GP exhibited notable selectivity and promising results in tea samples, achieving recovery rates of 102–107% for EC and 101.7–106% for TH.