DETERMINATION OF CEPHAPIRIN AND CEFTIOFUR RESIDUES IN BOVINE-MILK BY LIQUID-CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION

A method capable of quantitating cephapirin at a level of 20 ng/mL and ceftiofur at a level of 50 ng/mL was developed for raw bovine milk. R aw bovine milk is deproteinated with acetonitrile. The supernatant is collected and then acetonitrile is removed under reduced pressure whil e warming in a water bath at 40 degrees-50 degrees C. The extract is m ixed with water and loaded onto a conditioned C-18 solid-phase extract ion column. Analytes are eluted with acetonitrile, which is removed co mpletely under a stream of nitrogen gas. Analytes are separated from c oextractives by gradient elution with an ion-pair mobile phase on a re versed-phase column and are detected by ultraviolet absorbance at 290 nm. Mean recoveries from fortified milk samples ranged from 79 to 87% for cephapirin and from 76 to 86% for ceftiofur, with intralaboratory coefficients of variation ranging of 6-10% and 7-14%, respectively.