Detection of Tetracycline Antibiotics in Water by Dispersive Micro-solid Phase Extraction using Fe _\textbf3 O _\textbf4 @Cu _\textbf3 (btc) _\textbf2 Magnetic Composite Combined with Liquid Chromatography-Tandem Mass Spectrometry

Residues of tetracycline antibiotics (TCs) in environments may be harmful to human. Due to their high polarities, it is extremely challenging to efficiently enrich TCs with low concentrations in natural waters for analysis. In this work, a magnetic metal-organic framework Fe _3 O _4 @Cu _3 (btc) _2 was synthesized and applied as a dispersive micro-solid phase extraction adsorbent for TCs enrichment. Effects of dispersive micro-solid phase extraction conditions including extraction time, solution pH, and elution solvent on the extraction efficiencies of TCs were investigated. Results show that TCs could be enriched efficiently by Fe _3 O _4 @Cu _3 (btc) _2 , and electrostatic interaction between TCs and Fe _3 O _4 @Cu _3 (btc) _2 dominated this process. Combined with liquid chromatography-tandem mass spectrometry, four TCs residues (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) in natural waters were determined. The detection limits (LOD, S/N = 3) of the four antibiotics were 0.01-0.02 \mu g/L, and the limits of quantitation (LOQ, S/N = 10) were 0.04-0.07 \mu g/L. The recoveries obtained from river water and aquaculture water spiked with three TCs concentration levels ranged from 70.3% to 96.5% with relative standard deviations of 3.8%-12.8%. Results indicate that the magnetic metal-organic framework based dispersive micro-solid phase extraction is simple, rapid and high-loading for antibiotics enrichment from water, which further expand the practical application of metal-organic frameworks in sample pretreatment for environmental pollutant analysis.