Determination of trace antibiotics in water and milk via preconcentration and cleanup using activated carbons

CPAC-SPE-HPLC (coconut powdered activated carbon -SPE- HPLC) has been developed for the determination of antibiotic (ABX), sulfamonomethoxine sodium (SMM), oxytetracycline (OTC), ceftiofur hydrochloride (CEF) and marbofloxacin (MAR), in water and milk. Over 99.0% SMM and OTC were recovered from 20 mL of 0.5 μg/mL ABX solution using 10 mg-CPAC for adsorption and 2 mL of 30% NH₄OH/EtOH (1/19 v/v) for elution. Similarly, over 99.0% CEF and MAR were recovered using 15 mg-CPAC and 2 mL of 30% NH₄OH/n-PrOH (1/19 v/v). Moreover, the recovery efficiencies of various ABX from 5 to 80 mL of 0.02-2.00 μg/mL medicated milk containing 10 mM EDTA are ordered as follows: OTC (99.3%), SMM (99.1%) > CEF (68.9%) > MAR (61.4%). No interference towards HPLC analysis were observed with elution using 2 mL of 30% NH₄OH/EtOH (1/19 v/v). Furthermore, much lower limit of detections (0.02 μg/mL) than the maximum residual limits from European Commission (0.075-0.100 μg/mL) were obtained.