Determination of antibiotic residues in manure by liquid chromatography-tandem mass spectrometry coupled with solid phase extraction

A method was developed for the simultaneous determination of tetracyclines (TCs), quinolones (QUs) and sulfadimidine (SM2) in pig manure and chicken dung by a combined high performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) detection coupled with solid phase extraction. The residual antibiotics in manure were extracted with the mixture of methanol, acetic acid and water with the volume ratio of 6 : 3 : 1, enriched and purified by a hydrophilic lipophilic balance (HLB) solid-phase extraction cartridge. The C-18 chromatographic column was used to complete the separation of the analytes which were detected in multiple reaction monitoring (MRM) mode via positive electrospray ionization (ESI+). The external standard calibration curves were used for the quantification. All the antibiotics were determined with an excellent linear relationship from 50 to 1000 mu g/L for TCs and QUs, and from 5 to 100 mu g/L for SM2. The limits of detection for TCs, QUs and SM2 were 0.25-7.18, 0.15-3.16 and 0.04 mu g/kg, respectively. The recoveries of TCs, QUs and SM2 in pig manure and chicken dung were 40%-124% at the spiked levels from 0.1 to 10 mu g/g (RSDs ranged from 3.0% to 9.5%, n = 6). The method was successfully applied to determine the antibiotics in pig manure and chicken dung samples. The method has high accuracy and sensitivity for the determination of TCs, QUs and SM2 in pig manure and chicken dung.