Determination of veterinary antibiotics in dairy manure slurry

Veterinary antibiotics are used in dairy animal for growth promotion, sub-therapeutic or prophylactic and therapeutic purposes to better absorb nutrients and treat different diseases. In this study, four veterinary antibiotics named monensin, salinomycin, amprolium and lincomycin are selected. Monensin, salinomycin, amprolium are known as ionophores or anticoccidants belong to the class of emerging contaminants in the environment. When these veterinary antibiotics are used in dairy animal, they are excreted at high concentration in dairy manure and disposed to the environment by the land application of dairy manure as fertilizers. There is an increasing concern regarding the bacterial resistant to antibiotics in environment. Studies report several health and environmental effects of veterinary antibiotics. Therefore it is important to determine the concentration of veterinary antibiotics in different environmental matrices. Studies report the lack of suitable and reliable analytical method to determine veterinary antibiotics in different environmental matrices. Therefore, the prime objective of this study was the determination of veterinary antibiotics (monensin, salinomycin, amprolium and lincomycin) in a complex environmental matrix such as dairy manure slurry. This study describe a high performance liquid chromatography triple quadrupole mass spectrometer (HPLC-MS/MS) method developed for the quantification of monensin, salinomycin, amprolium and lincomycin in background dairy manure sample. Selected veterinary antibiotics standard were spiked in dairy manure slurry sample and developed extraction procedures were applied for recovery studies. The results show that monensin, salinomycin, amprolium and lincomycin were not used in dairy animal of sampled dairy farm. The extraction recovery results show that the average recoveries of monensin were 117.6 ± 3.2%, 123 ± 1.1% and 124.6 ± 1.0% with spike concentration of 10, 5 and 1 mg/L respectively; being the highest among all four selected veterinary antibiotics. In contrast, the average recoveries of lincomycin were the lowest among all four selected veterinary antibiotics. The average recoveries of lincomycin were 68.3 ± 0.3%, 89 ± 1.5% and 98.7 ± 0.9% with spike concentration of 10, 5 and 1 mg/L respectively. Results also show that the extraction recoveries of salinomycin were 81.9 ± 0.8%, 105 ± 1.8% and 111.8 ± 0.1% with spike concentration of 10, 5 and 1 mg/L respectively. While the amprolium recoveries were 114.6 ± 2.6%, 155 ± 2.5% and 104 ± 6.2% with spike concentration of 10, 5 and 1 mg/L respectively. The extraction recovery results also reflect that the average recoveries of selected veterinary antibiotics except amprolium were increasing with decreasing of spike concentration of veterinary antibiotics. Therefore study's results conclude that the developed HPLC-MS/MS method was successful in quantifying veterinary antibiotics in dairy manure and developed extraction procedures were suitable for the extraction of selected veterinary antibiotics from dairy manure.