title: Liquid chromatographic determination of tilmicosin in swine feed at 200-400 mg/kg level: interlaboratory study.
abstract: An analytical method for the determination of tilmicosin at 200-400 mg/kg, the intended use concentration range, was evaluated in an interlaboratory study involving 5 laboratories, including the sponsor. The interlaboratory study evaluated the intra- and interlaboratory precision and accuracy of a tilmicosin feed method. The method procedure involved extracting tilmicosin from feed by adding 200 mL extractant to 20 g feed and shaking for 1 h. The extract is filtered and analyzed by gradient liquid chromatography which separates tilmicosin from feed matrix in 30 min. Each laboratory assayed 5 replicates of fortified feed at concentrations of 0, 100, 200, 400, and 600 mg/kg. The mean recovery among fortified samples ranged from 81.4 to 98.8%, with a percent coefficient of variation (%CV) ranging from 0.3 to 4.0%. For all blank control feed samples no significant interferences were observed. In addition, each laboratory assayed 5 replicates of medicated feed samples prepared at 2 levels (200 and 400 mg/kg) with either a horizontal or vertical mixer. Along with the medicated feed samples were included 5 replicates of a blank control feed. The identities of the medicated and blank control feed samples were blinded to the analysts. The results for the medicated feed samples ranged from 95.8 to 106% of label claim, with a %CV ranging from 2.1 to 6.7%.
authors.affiliation: Elanco Animal Health, A Division of Eli Lilly and Co., Greenfield, IN 46140, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Readnour
authors.forename: M R
authors.initials: MR
authors.lastname: Coleman
authors.forename: M G
authors.initials: MG
authors.lastname: Leadbetter
mesh_terms: D000821:Animal Feed; D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis*; D002853:Chromatography, Liquid; D019411:Clinical Laboratory Techniques; D005506:Food Contamination; D018942:Macrolides; D015394:Molecular Structure; D011786:Quality Control; D015203:Reproducibility of Results; D013552:Swine; D015645:Tylosin / Q000031:analogs & derivatives* / Q000032:analysis
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; C052319:tilmicosin; D015645:Tylosin