Development of a modified QuEChERS method for the determination of veterinary antibiotics in swine manure by liquid chromatography tandem mass spectrometry.

A QuEChERS (quick, easy, cheap, effective, rugged and safe) based methodology was developed for the rapid, simultaneous quantification and identification of 26 veterinary drugs in swine manure by liquid chromatography tandem mass spectrometry. The selected antibiotics included tetracyclines, sulfonamides, macrolides, fluoroquinolones, lincosamides and pleuromutilins. This is the first study to determine pleuromutilin levels in manure. The QuEChERS process involved two simple steps. First, sample extraction with methanol: acetonitrile: 0.1M EDTA-McIlvaine buffer followed by phase separation with MgSO4: NaCl addition. The supernatant was then extracted and cleaned by dispersive solid-phase extraction using a primary-secondary amine (PSA) and octadecylsilane (C18) support. The proposed method provides a linearity in the range of 1-500ngmL-1 and linear regression coefficients (r) were greater than 0.996. MDL and MQL ranged between 0.01-1.86µgkg(-1) and 0.05-5.91µgkg(-1), respectively. Recoveries ranged from 61.39 to 105.65% with the exception of sulfaquinoxaline (55.7-56.8%) and valnemulin (33.7-37.7%). This method resulted in good precision (repeatability and reproducibility) and relative standard deviations less than 17% within the same day, and lower than 20% between days. The method was then applied to study the swine manure samples collected from Guangdong, China. Chlortetracycline, tetracycline, doxycycline, sulfadimidine and tilmicosin were detected in all samples indicating high residuals in manure. In fact tilmicosin was detected at 14400µgkg(-1) suggesting that prudent treatment of manure should be conducted to prevent environmental contamination. In conclusion, this workflow can provide a simpler and more cost-effective alternative to conventional methods and is compatible with processing large sample numbers over a short time period.

Metabolism of nitazoxanide in rats, pigs, and chickens: Application of liquid chromatography coupled to hybrid linear ion trap/Orbitrap mass spectrometer.

Nitazoxanide (NTZ) is a nitrothiazole benzamide compound with a broad activity spectrum against parasites, Gram-positive and Gram-negative anaerobic bacteria, and viruses. In this study, hybrid linear ion trap/Orbitrap mass spectrometer providing a high mass resolution and accuracy was used to investigate the metabolism of NTZ in rats, pigs, and chickens. The results revealed that acetylation and glucuronidation were the main metabolic pathways in rats and pigs, whereas acetylation and sulfation were the major metabolic pathways in chickens, which indicated interspecies variations in drug metabolism and elimination. With the accurate mass data and the characteristic MS(n) product ions, we identified six metabolites in which tizoxanide and hydroxylated tizoxanide were phase I metabolites and tizoxanide glucuronide, tizoxanide glucose, tizoxanide sulfate and hydroxyl tizoxanide sulfate were phase II metabolites. Hydroxylated tizoxanide and tizoxanide glucose were identified for the first time. All the comprehensive data were provided to make out the metabolism of NTZ in rats, pigs and chickens more clearly.