title: Liquid chromatographic determination of oxytetracycline in bovine plasma by double-phase extraction.
abstract: A liquid chromatographic method for the determination of oxytetracycline in bovine plasma was developed. Contrary to most current tetracycline assays involving solid-phase extraction, oxytetracycline and the internal standard tetracycline were isolated from buffered plasma by double-phase extraction with ethyl acetate-isopropyl alcohol. The latter component was found to be essential to ensure reproducible partitioning of both tetracyclines into the organic layer. Chromatography was conducted on a Lichrosorb RP8 column, compounds were eluted with 0.01 M oxalic acid-methanol-acetonitrile, and detection was at 357 nm. Linearity was observed over the 0-8.5-micrograms/mL range, and the detection limit approximated 5 ng/mL. The extraction yield was 80.4 +/- 3.4% (n = 12), and the coefficients of variation for repetitive within-run and between-run analyses at two concentration levels (0.25 and 2 micrograms/mL) were 1.0-4.3 and 2.4-7.2%, respectively. The method was applied to a pharmacokinetic study of oxytetracycline in three nonlactating cows after a single intramuscular administration of a long-acting preparation.
authors: Laboratoria voor Medische Biochemie en voor Klinische Analyse, Ghent, Belgium.
authors: H J
authors: HJ
authors: Nelis
authors: J
authors: J
authors: Vandenbranden
authors: A
authors: A
authors: De Kruif
authors: F
authors: F
authors: Belpaire
authors: A P
authors: AP
authors: De Leenheer
mesh_terms: D000433:1-Propanol; D000085:Acetates; D000818:Animals; D002417:Cattle; D002623:Chemistry Techniques, Analytical / Q000379:methods; D002853:Chromatography, Liquid; D005260:Female; D010118:Oxytetracycline / Q000097:blood*
chemical_list: D000085:Acetates; C007650:ethyl acetate; D000433:1-Propanol; D010118:Oxytetracycline