Growth ZIF-8 on carbon cloth for electric field enhanced thin film microextraction of tetracyclines in milk and honey

Tetracyclines (TCs) are a prevalent type of broad-spectrum antibiotic, which could pose a great threat to human health. Herein, ZIF-8 modified carbon cloth (ZIF-8/CC) for electric field-enhanced thin-film microextraction (EE-TFME) of TCs (oxytetracycline, tetracycline and doxycycline) was developed. ZIF-8/CC was prepared by growing ZIF-8 in situ on the surface of CC as the positive electrode of EE-TFME. Compared to the bare carbon cloth electrode, the ZIF-8/CC electrode can enhance the TCs extraction capacity up to nearly twice. Furthermore, EE-TFME could reduce the extraction equilibrium time from 30 min to 20 min. The detection limit of combined high performance liquid chromatography (HPLC) was 2.0-2.5 ng/mL, and the RSDs of intra-day and inter-day were all below 7.1%. The EE-TFME-HPLC method developed based on ZIF-8/CC can be successfully applied to detection of TCs in honey and milk. The spiked recovery experiments of 50 ng/g and 100 ng/g were carried out on milk and honey samples, and the recovery rate of all TCs was between 82.4% and 102.9%, RSDs were less than 8.2%.