Ion-pair liquid chromatographic determination of some penicillins in canine and equine sera

A sensitive liquid chromatographic method was developed for determining oxacillin, cloxacillin, and dicloxacillin (simultaneously), and penicillin G, amoxicillin, carbenicillin, and ticarcillin in canine and/or equine serum. The method involves filtering diluted serum through a 30,000 molecular weight cut-off filter and separating penicillins from other serum components by ion-pair liquid chromatography using a reverse-phase column eluted with acetonitrile-water solutions. The ultraviolet absorbance of the column effluent was monitored at 230 nm. Recoveries of oxacillin, cloxacillin, dicloxacillin, and penicillin G (spiked at 2.5 micrograms/mL), amoxicillin (spiked at 5 micrograms/mL), and carbenicillin and ticarcillin (spiked at 10 micrograms/mL) from canine and equine serums ranged from 78.3 to 104.4% with coefficients of variation ranging from 3.35 to 5.95%. The limit of detection for these penicillins was 0.02-0.05 microgram/mL.