Determination of fluoroquinolones in chicken feces – A new liquid–liquid extraction method combined with LC–MS/MS

•Suitable method for the detection of fluoroquinolones in the sub μg/kg range in chicken feces.•Highest analyte recoveries were achieved using dichloromethane as extraction solvent.•The use of EDTA is advisable to increase recovery and decrease matrix interactions.•High enrofloxacin amounts were excreted after a treatment with 10 mg/kg bodyweight.•Intake of antibiotics below therapeutic dosages e.g. via dried feces particles is discussed.

The application of antibiotics including fluoroquinolones to farming animals is widespread and may lead to the development of antibiotic resistance and other environmental effects. To calculate environmental loads and for a proper risk assessment it is necessary to determine the antibiotic concentration in feces. Therefore, a new liquid–liquid extraction method combined with HPLC–MS/MS for the detection of marbofloxacin, ciprofloxacin, enrofloxacin and difloxacin in chicken feces was developed. Recoveries ranged from 51.0% to 83.5%. LOQs were between 0.10 and 1.09 μg/kg. Feces of chickens treated with an enrofloxacin dosage of 10 mg/kg bodyweight revealed maximum enrofloxacin and ciprofloxacin concentrations of 61.3 and 18.8 mg/kg. Both antibiotics could be detected in feces up to two days after the last application in notable amounts (∼1 mg/kg). Thus, feces of recently medicated chickens should not be used as a fertilizer without any further processing.