OPTICAL IMMUNOBIOSENSOR ASSAY FOR DETERMINING ENROFLOXACIN AND CIPROFLOXACIN IN BOVINE-MILK

A rapid, sensitive optical immunobiosensor assay was developed and use d to determine enrofloxacin and its main metabolite, ciprofloxacin, in milk from healthy cows and cows with clinical signs of mastitis after intramuscular administration of enrofloxacin. Liquid chromatography ( LC) was used to confirm results of the biosensor assay. Despite incomp lete cross-reactivity between polyclonal enrofloxacin antibodies and c iprofloxacin, the biosensor assay could be used for semiquantitative a nalysis of the sum of the 2 substances. LC analysis showed that ciprof loxacin persisted at levels exceeding the expected future maximum resi due limit in milk for several days after the end of the withdrawal per iod.