Sensitive detection of furazolidone and nitrofurantoin by fluorescent nanoprobe coated with 3-mercaptopropionic acid on CdS quantum dots

Cadmium sulfide quantum dots (CdS QDs) were synthesized with 3-mercaptopropionic acid (MPA) as protective agent, which were characterized by TEM, UV-vis, fluorescence, XRD and TGA. Based on the fluorescence quenching of 3-MPA-CdS QDs, the indirect methods for the determination of furazolidone (FZD) and nitro-furantoin (NFT) were established. The interaction between FZD/NFT and CdS QDs was investigated by using fluorescence, resonance light scattering, UV-vis and FT-IR. The analyses of Stern-Volmer and fluorescence lifetime indicated that the two quenching systems were all static. The binding constant (Ka) of FZD/NFT-CdS QDs was 1.20 x 104/1.81 x 104 L/mol at 293 K, respectively. Hydrogen bond or van der Waals force was the main binding force between CdS QDs and drugs. Under optimum experimental conditions, the concentration of FZD/ NFT was respectively highly correlated with the fluorescence intensity ratio in the range of 0.27 - 36.03/0.57 - 28.58 mu g mL-1. The interference experiments showed that the methods had good selectivity. The limit of detection (LOD) for FZD/NFT was 0.02/0.01 mu g mL-1. The contents of FZD and NFT in fish samples were determined, and the recoveries were 97.41-99.52 % and 96.64-100.49 %, respectively.