Determination Of Cefquinome Residues By HPLC And Its Residue Depletion In Milk

At present, the dairy cow mastitis has become a major problem that seriously affects the value of dairy production. Cefquinome (CEF) is the forth generation of cephalosporins which can inhibit cell wall synthesis to achieve bactericidal effects, with a broad antibacterial spectrum and powerful bactericidal actions, and can reach a higher breast tissue concentration. Cefquinome has been registered in China to be used in animals. It is generally used to treat E.coli-induced cow mastitis, Pasteurellosis-induced or Actinobacillus pleuropneumoniae-induced porcine respiratory disease clinically. The study developed a method for determination of residual cefquinome and researched the depletion regulation of a cefquinome sulfate injection in milk, in order to establish a reasonable milk withdrawl time.1. Determination of residual cefquinome in milk: Samples were extracted using acetonitrile. The extracted solution was evaporated to dry and added flowing phase. The flowing phase was acetate buffer (pH3.6)–mathanol (83:17); detection wavelength was 270 nm. Under these chromatography conditions, cefquinome concentration in milk had a good liner coefficient relation (R2≥0.9997) in the range of 0.02~2μg/ml. The average recoveries at 0.02μg/ml,1μg/ml,2μg/ml levels in milk were 85.28%~98.56%. The within-day CV and between-day CV were 1.55%~4.36% and 0.40%~2.01% respectively. The lowest detectable limit was 0.01μg/ml, and the detection quantity was 0.02μg/ml.2. Residural depletion of a cefquinome sulfate injection in milk: Four healthy adult Holstein cows which were not used cefquinome before, were used in residural depletion studies. The cows were intramuscularly injected cefquinome sulfate suspention: 2 ml/50kg b.w., once a day, for two days. The milk samples were collected at a given time point after adminstration. Cefquinome concentrations in milk were determinted by an established method above. The results indicated that the CEF concentration reached its peak at 24h, fell below 0.02μg/ml at 84h, all below the detection limit 0.01μg/ml at 96h. So the milk withdral time of this drug can be adviced as 4 days.