Determination of Multi-class Antibiotic Residues in Compost by Microwave-enhanced Accelerated Solvent Extraction and Ultra Performance Convergence Chromatography with Tandem Mass Spectrometry

This work reports the development and application of a multi-class compound analysis method for the determination of 20 antibiotic residues in compost. Samples were processed by microwave-enhanced accelerated solvent extraction at 120°C for 7.5 min. Salting-out homogeneous liquid-liquid extraction was used to remove water and water-soluble impurities from the extract before ultra performance convergence chromatography with tandem mass spectrometry analysis. By using the supercritical fluid (carbon dioxide) and organic solvent (methanol) as the mobile phase, the 20 antibiotics and the internal standard were well separated in 8.2 min without obvious matrix effect. Method validation was performed and good trueness (relative error in the range of ±5.0%) and precision (inter- and intraday relative standard deviations < 10.8%) were obtained. Method detection and quantitation limits were 0.8-1.9 and 2.7-7.1 ng/g, respectively. Recoveries were assessed at three concentration levels (10, 60, and 400 ng/g) and acceptable mean values (70.4-111.9%) were found. This method has also been used to analyze real samples, and the average concentrations of antibiotics (excepting the concentrations < method quantitation limits) were determined up to 123.6 ng/g. The results showed the method could be helpful for the analysis of multi-class antibiotics in environmental samples.