Rapid and Sensitive Detection of Rutin in Food Based on Nitrogen-Doped Carbon Quantum Dots as Fluorescent Probe

The aim of this study was to establish a rapid detection method of rutin in food based on nitrogen-doped carbon quantum dots (N-CDs) as the fluorescent probe. N-CDs were prepared via a single-step hydrothermal process using citric acid as the carbon source and thiourea as the nitrogen source. The optical properties of N-CDs were characterized using an electron transmission microscope, X-ray diffractometer, Fourier-transform infrared spectrometer, and nanoparticle size potential analyzer. The UV/Vis absorption property and fluorescence intensity of N-CDs were also characterized using the respective spectroscopy techniques. On this basis, the optimal conditions for the detection of rutin by N-CDs fluorescent probes were also explored. The synthesized N-CDs were amorphous carbon structures with good water solubility and optical properties, and the quantum yield was 24.1%. In phosphate-buffered solution at pH = 7.0, Rutin had a strong fluorescence-quenching effect on N-CDs, and the method showed good linearity (R2 = 0.9996) when the concentration of Rutin was in the range of 0.1–400 μg/mL, with a detection limit of 0.033 μg/mL. The spiked recoveries in black buckwheat tea and wolfberry were in the range of 93.98–104.92%, the relative standard deviations (RSD) were in the range of 0.35–4.11%. The proposed method is simple, rapid, and sensitive, and it can be used for the rapid determination of rutin in food.