A high-throughput screening method for determination of multi-antibiotics in animal feed

A high-throughput method based on ultrasonic-assisted extraction, 96-well plate thin-film microextraction was established to determinate 18 antibiotics in animal feed. In this method, the extraction was implemented by ultrasonic-assisted extraction for 30 min with disodium ethylenediaminetetraacetic acid-McIlvaine buffer (pH 5) containing 6% sodium chloride w/v, purified by thin-film microextraction and combined with 96-well plate system to improve the efficiency. Optimization of thin-film microextraction conditions was performed by methods of single factor and response surface, and finalized as: condition time: 20 min; adsorption time: 55 min; washing time: 5 s with water; desorption time: 30 min with acetonitrile/water (8:2, v/v) containing 0.1% formic acid v/v. Evaluation of different extractive phases showed that polystyrene-divinylbenzene-polyacrylonitrile was the optimum coating. The analysis was performed by ultra-high performance liquid chromatography with tandem mass spectrometry. Recovery, inter- and intraday precision, linearity, limit of detection, and quantitation were evaluated. The average recoveries of 18 antibiotics were 66.6-93.5% at three spiked levels, intraday precision was 1-8.4%, and interday precision was 3.0-16.4%. The linearity was good for r²  > 0.99. Limits of detection and quantification were found in the range of 1-14 and 4-48 µg/kg, respectively.