title: Development of multiclass methods for drug residues in eggs: silica SPE cleanup and LC-MS/MS analysis of ionophore and macrolide residues.
abstract: A method was developed that is suitable for screening eggs for a variety of nonpolar residues in a single procedure. Residues are extracted by silica solid-phase extraction (SPE). Analysis is conducted via reverse-phase gradient liquid chromatography, electrospray ionization, and tandem ion trap mass spectrometry. For screening purposes (based on a single precursor-product ion transition) the method can detect ionophore (lasalocid, monensin, salinomycin, narasin) and macrolide (erythromycin, tylosin) residues in egg at approximately 1 ng/mL (ppb) and above and novobiocin residues at approximately 3 ppb and above. Conditions are described for confirmatory analysis based on multiple ions in the product ion spectrum. The extraction efficiency for ionophores was estimated at 60-85%, depending on drug. Recovery of macrolides and novobiocin was not as good (estimated at 40-55% after a hexane wash of the final extract was included), but the method consistently screened and confirmed these residues at concentrations below the target of 10 ppb. The method was applied to eggs from hens dosed with each drug individually. Lasalocid was found to have the highest probability of detection in eggs based on its high ionization efficiency and higher rate of deposition relative to the other drugs. The method is part of a larger scheme to provide surveillance methods for a wide variety of drug residues in eggs.
authors.affiliation: Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland 20708, USA. dheller@cvm.fda.gov
authors.forename: David N
authors.initials: DN
authors.lastname: Heller
authors.forename: Cristina B
authors.initials: CB
authors.lastname: Nochetto
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D004350:Drug Residues / Q000032:analysis*; D004531:Eggs / Q000032:analysis*; D007476:Ionophores / Q000032:analysis*; D018942:Macrolides / Q000032:analysis*; D013058:Mass Spectrometry / Q000379:methods*; D015203:Reproducibility of Results; D012822:Silicon Dioxide
chemical_list: D007476:Ionophores; D018942:Macrolides; D012822:Silicon Dioxide