The water-soluble CdTe/CdS quantum dots (QDs) was synthesized using mercaptoacetic acid as stabilizer. A novel method for determination of sparfloxacin (SPFX) has been developed based on quenching of the fluorescence of CdTe/CdS QDs at 580 nm by SPFX in aqueous solutions. Interaction of CdTe/CdS QDs synthesized in aqueous solution with sparfloxacin was studied by fluorescence spectrum and absorption spectrum. The mechanism of fluorescence quenching belongs to static quenching. IR spectrometer results indicated that the mechanism of the reaction was likely to be that the changes of surface-bound organic molecules of QDs, were induced by sparfloxacin, and the Te-oxygen complex was formed at the Cd surface vacancies. The optimum reaction conditions was found to be at pH 6.50 with phosphate buffer solution, and a CdTe/CdS QDs concentration of 3.75×10^－4 mol/L. The quenched fluorescence intensity of CdTe/CdS QDs was linearly proportional to the concentration of SPFX from 0.1 to 50 μg/mL with correlation coefficient r＝0.9992, and the detection limit for SPFX was 0.01399 μg/mL. The amounts of SPFX in pill were determined by the proposed method and the results agreed with the claimed value. Trace amounts of SPFX in milk were also determined with the recovery of 93.1%～102.4%.

Key words: CdTe/CdS quantum dots, fluorescent probe, sparfloxacin, residue determination