Quantification of Cephapirin in Dairy Cow Feces and Urine using Solid Phase Extraction (SPE) coupled with Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC/MS/MS)

Abstract Text: Antibiotic use in animal agriculture has been under scrutiny for two decades because of the persistency of excreted antibiotics in the environment and their potential contribution to bacterial antibiotic resistance. Cephapirin, a cephalosporin antibiotic, is commonly used for dry cow therapy and other therapeutic treatments in dairy cows. Fecal and urinary excretion of cephapirin could introduce this compound into the environment with land application of manure or runoff from the feedlot or barnyard. To date, however, the environmental loading of cephapirin by the livestock industry remains un-assessed, largely due to a lack of appropriate analytical methods. Therefore, an analytical method was developed and validated to qualify and quantify cephapirin in dairy cow feces and urine. The method includes extraction with phosphate buffer (0.05 M) and methanol at 50:50 (v/v) followed by solid-phase extraction (SPE) clean-up via elution through hydrophilic-lipophilic-balanced cartridges and filtering through 0.2 μm filters. Cephapirin in clarified sample extracts was qualified and quantified using ultra performance liquid chromatography-tandem mass spectrometry (UPLC/MS/MS). The limit of quantification (LOQ) of the developed method was 4.02 ng/g and 0.96 ng/mL for feces and urine, respectively. Recovery of cephapirin from spiked blank feces and urine was 64 to 73% and 81 to 84%, respectively. Intra- and inter-day variation [residual standard deviation (RSD), %] were used to estimate repeatability and reproducibility of the method, and ranged from 7.9 to 8.2% for feces and 3.07 to 9.59% for urine. This method was applied to feces and urine collected from dairy cows within 8 hours of cephapirin administration. Trace amounts (ng/g) of the compound were detected in feces and very high concentrations (133 to 480 ng/mL) in urine. The described method is sensitive, accurate, and robust and will advance understanding of the fate and environmental impact of antibiotics used on farms.

Keywords: Cephapirin, dairy cow feces and urine, ultra performance liquid chromatography-tandem mass spectrometry