title: Interlaboratory comparison of methods for the determination of incurred tilmicosin residues in bovine liver.
abstract: The objective of this study was to compare 2 methods for the determination of tilmicosin residues in bovine liver samples. Three laboratories participated in the comparison of the 2 methods. The first method was described in a New Animal Drug Application (NADA 140-929), and the second was a modification of that method in which hexane was substituted for carbon tetrachloride in one cleanup step. Each of the 3 laboratories analyzed subsamples of 10 bovine livers containing incurred tilmicosin. Residues ranged from 2.3 to 81 ppm tilmicosin in the 10 liver samples with an 11.8% relative standard deviation obtained by using both methods. In addition, fortified-control liver tissue samples were analyzed concurrently with tissues containing incurred residues by using the modified method in one of the laboratories. The fortification levels ranged from 0.3 to 112 ppm, with recoveries ranging from 76 to 92%. The results from the 3 laboratories were comparable, indicating that the modified method was not only as effective as the original NADA method, but also more desirable because of the change to a less hazardous solvent.
authors.affiliation: U.S. Food and Drug Administration, Denver, CO 80225, USA. sclark1@ora.fda.gov
authors.forename: Susan B
authors.initials: SB
authors.lastname: Clark
authors.forename: John J
authors.initials: JJ
authors.lastname: O'Rangers
authors.forename: W Douglas
authors.initials: WD
authors.lastname: Rowe
authors.forename: Mark R
authors.initials: MR
authors.lastname: Madson
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hurlbut
authors.forename: John N
authors.initials: JN
authors.lastname: Sofos
authors.forename: Brenda
authors.initials: B
authors.lastname: Fuerst
authors.forename: Glenda
authors.initials: G
authors.lastname: James
authors.forename: Sydney
authors.initials: S
authors.lastname: Griffith
authors.forename: Robin S
authors.initials: RS
authors.lastname: Readnour
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis*; D002417:Cattle; D004350:Drug Residues; D007202:Indicators and Reagents; D008099:Liver / Q000737:chemistry*; D018942:Macrolides; D012996:Solutions; D015645:Tylosin / Q000031:analogs & derivatives* / Q000032:analysis*
chemical_list: D000900:Anti-Bacterial Agents; D007202:Indicators and Reagents; D018942:Macrolides; D012996:Solutions; C052319:tilmicosin; D015645:Tylosin