Determination of sparfloxacin with CdSe/CdS quantum dots as fluorescent probes

Water-soluble CdSe/CdS quantum dots (QDs) modified with thioglycolic acid (TGA) were synthesized. A novel method for determination of sparfloxacin (SPFX) has been developed based on quenching of the fluorescence of QDs at 556 nm wavelength. The optimum fluorescence intensity was found in 0.067 mol L−1 KH2PO4-Na2HPO4 buffer solution at pH 6.47 of 3.0×10−5 mol L−1 QDs. When the concentration of quantum dots is 3.0×10−5 mol L−1 the fluorescence quenching intensity of QDs is linearly proportional to the concentration of SPFX from 0.5 μg mL−1 to 30 μg mL−1, with correlation coefficient R=0.9983. The detection limit for SPFX was 0.1391 μg mL−1. The method was used for determination of SPFX in tablets, and the results agreed with the claimed value. Trace amounts of SPFX in milk were also determined with the recovery of 95.3-106.8%.