title: Liquid chromatographic method to determine narasin in feedingstuffs and premixtures: development, validation, and interlaboratory study.
abstract: A reversed-phase liquid chromatography (LC) method for narasin in feedingstuffs and premixtures was developed, validated, and interlaboratory studied. The extraction solvent was methanol-K2HPO4 solution (9 + 1, v/v). Narasin was detected at 600 nm after post-column derivatization with dimethylamino-benzaldehyde. Recovery was >90%. The repeatability (RSDr) in feed (20-140 mg/kg) ranged between 1.2 and 10.5%; the within-laboratory reproducibility (RSD(R)) ranged between 2.2 and 4.9%. The limit of determination was <20 mg/kg. Other feed additives did not interfere in the assay. The method showed ruggedness against changes in the composition of extraction solvent, eluent, and conditions for post-column reactions. In an interlaboratory study, 5 broiler feeds (4 positive, 1 blank) and 1 premixture were analyzed by 13 laboratories. The RSDr of the feedingstuffs (20-120 mg/kg) varied between 2.17 and 7.57%. The HORRAT ranged between 0.77 and 0.88, with recoveries between 82 and 104%. One laboratory detected small signals in the blank sample, calculated as 0.6 and 2.8 mg/kg. For the premixture, acceptable results for reproducibility could only be obtained after modification of the method: the RSDr was 4.42% and the HORRAT was 1.56 (12 laboratories).
authors.affiliation: State Agricultural Testing and Research Station Augustenberg (LUFA), 76227 Karlsruhe, Germany.
authors.forename: Alfred
authors.initials: A
authors.lastname: Thalmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Wagner
authors.forename: Marinka
authors.initials: M
authors.lastname: Tomassen
authors.forename: Jaap
authors.initials: J
authors.lastname: Driessen
authors.forename: Jacob
authors.initials: J
authors.lastname: de Jong
mesh_terms: D000465:Algorithms; D000821:Animal Feed / Q000032:analysis*; D001681:Biological Assay; D002138:Calibration; D003049:Coccidiostats / Q000032:analysis*; D005062:European Union; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D011714:Pyrans / Q000032:analysis*; D012015:Reference Standards; D015203:Reproducibility of Results; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D014465:Ultrasonics
chemical_list: D003049:Coccidiostats; D007202:Indicators and Reagents; D011714:Pyrans; D012997:Solvents; C013612:narasin