Pg. Schermerhorn et al., DETERMINATION OF CEPHAPIRIN AND CEFTIOFUR RESIDUES IN BOVINE-MILK BY LIQUID-CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION, Journal of AOAC International, 81(5), 1998, pp. 973-977
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.