Rapid Quantitation of Doxycycline Hydrochloride, Metronidazole and Sulfadimidine in Pork and Milk Using PCN-225 Fluorescence Assay

To explore a simple, rapid and sensitive method for the detection of doxycycline hydrochloride (DOX), metronidazole (MTZ) and sulfadimidine (SM₂) in pork and milk, a porphyrinic zirconium metal-organic framework (MOF) material, PCN-225, was synthesized as a fluorescence probe and used to construct a fluorescence sensor to determine the concentrations of DOX, MTZ and SM₂. First, the morphology, structure and properties of PCN-225 were characterized and optimized, and the sensing mechanism of PCN-225 was analyzed by fluorescence spectroscopy and ultraviolet-visible (UVVis) absorption spectroscopy. Second, the sensing performance of PCN-225 for detecting the three antibiotics was studied. The results showed that the developed method showed excellent selectivity and sensitivity for the detection of DOX, MTZ and SM₂, with detection limits of 4.70, 5.30 and 4.84 nmol/L, respectively. Finally, the sensor was used to detect DOX, MTZ and SM₂ in pork and milk. The recovery rates ranged from 94.7% to 110.8%, with relative standard deviations (RSDs) not higher than 1.1%. In conclusion, this method shows great potential for the detection of DOX, MTZ and SM₂ in a simple, efficient, sensitive and rapid manner.