Copper-amino acid carbon dots with peroxidase-like activity combined with DLLME for colorimetric detection of butylated hydroxyanisole in edible oils

For the first time, copper-doped amino acid carbon dots (Cu/Asp-CDs) are reported as a green peroxidase-like nanozyme. Using Cu 2+ as the metal dopant and L-aspartic acid (Asp) as the ligand, Cu/Asp-CDs exhibit high catalytic activity and stability. They efficiently catalyze the oxidation of butylated hydroxyanisole (BHA) in the presence of 4-aminoantipyrine (4-AP) and H 2 O 2 , producing a visible color change for rapid and specific BHA detection. Based on this, a portable, cost-effective colorimetric sensor was developed, showing high sensitivity, selectivity, and linearity from 0.67 to 66.67 μM, with a detection limit of 0.27 μM. To extract BHA from edible oils, a deep eutectic solvent of choline chloride and thymol (1:2 molar ratio) was used in liquid–liquid microextraction, achieving recoveries of 89.0–109.0%. Combined with the nanozyme, this method enables a practical, rapid (within 20 min) assessment of synthetic antioxidants, offering a reliable tool for food quality monitoring.