One-Step Solvothermal Synthesis of Carbon Dots for Rapid and Accurate Determination of Hemin Content

The development of sensitive and specific methods for the high-quality analysis of hemin-related drugs is significant in the pharmaceutical field. In this work, a simple and rapid method based on the fluorescent properties of carbon dots (CDs) was established for the determination of hemin in drugs. By taking melamine and ethylenediamine as the reaction materials, the fluorescent CDs were synthesized by a one-step solvothermal method, which can be used for the determination of hemin in drugs by the fluorescent inner filter effect. The as-prepared fluorescent CDs with rich functional groups on the surface displayed good water solubility, strong salt resistance, robust pH stability, and photobleaching resistance. Most importantly, the fluorescent excitation wavelength of fluorescent CDs was very close to the absorption wavelength of hemin, providing the evidence for the fluorescent inner filter effect. When the hemin concentration was in the range of 0.01–1 μM, there was a good linear relationship between the hemin content with the fluorescence intensity of CDs. The linear regression equation was (1 − F/F₀) = 0.0897c + 0.0124, with a correlation coefficient (R²) of 0.9982 and a detection limit of 9 nM. This assay was successfully used to determine the content of hemin in the tablet, which displayed 97.9–105.5% of the labelled amount, with a relative standard deviation of less than 3%. The developed fluorescence method for the detection of hemin content displays the advantages of accurate, rapid, and high sensitivity, which could prove to be a useful tool for the determination of hemin supplement tablets.