Abstract: By in situ growing the metal-organic framework ZIF-8 on the surface of carbon cloth (CC), an electric field-enhanced thin-film microextraction (EE-TFME) electrode was prepared and combined with high performance liquid chromatography (HPLC) to develop a rapid and accurate analytical method for the determination of tetracycline antibiotics (oxytetracycline, tetracycline, and doxycycline) in animal-derived food products (honey and milk). The morphology, structure, and adsorption properties of ZIF-8/CC were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption isotherms. The results indicated that the prepared material exhibited favorable adsorption characteristics. Under optimal conditions, the developed method achieved extraction equilibrium within 20 min. It showed good linearity for the three tetracycline antibiotics in the concentration range of 8.0-200.0 ng/mL (R2 > 0.992). The limits of detection (LOD) and quantification (LOQ) were 2.0-2.5 and 8.0-8.5 ng/mL, respectively. In honey and milk samples, doxycycline was detected at trace levels (< LOQ). At spiked concentrations of 20, 50 and 100 ng/g, recoveries ranged from 81.5% to 103.0%, with relative standard deviations (RSD, n = 5) no more than 7.2%. The EE-TFME method based on ZIF-8/carbon cloth developed in this study can be applied to the detection of tetracycline antibiotics in animal-derived foods, providing an effective sample pretreatment approach for food safety monitoring.

Key words: thin-film microextraction; electric field-enhanced; high performance liquid chromatography; carbon cloth; tetracycline antibiotics