Rapid detection of chlortetracycline and metacycline in food based on the fluorescence quenching effect of ZnS@CdS quantum dots

Excessive accumulation of tetracycline can not only cause harm to the environment, but also threaten human health through the food chain. In order to reduce the likelihood of people being harmed by these drugs, new methods for the detection of chlortetracycline (CTC) and metacycline (MTC) based on the ZnS@CdS quantum dot (QDs) fluorescence quenching reaction were established. High quality CdS QDs capped by mercaptopropionic acid and ZnS were prepared, which were characterized by transmission electron microscopy, fluorescence, ultraviolet visible spectra, fourier transform infrared, X-ray diffraction and thermogravimetric analysis. The study showed that there was an interaction between CTC/MTC and ZnS@CdS QDs, and the electrostatic force was the main force. The Stern-Volmer analysis showed that the quenching was static, which was further proved by fluorescence lifetime experiment. Under the optimized experimental conditions, linear calibration curves for detecting CTC/MTC were obtained with a limit of detection of 12.91/12.10 ng mL−1. The contents of CTC/MTC in milk, tangerine, beef and pork samples were detected. The recoveries of CTC/MTC were satisfactory. The established method had good analytical performance and can be used for the detection of more actual samples.