title: Cold-temperature stability of five beta-lactam antibiotics in bovine milk and milk extracts prepared for liquid chromatography-electrospray ionization tandem mass spectrometry analysis.
abstract: The stability of five major beta-lactam antibiotics (amoxicillin, ampicillin, cloxacillin, oxacillin, and penicillin G) in fortified milk and in milk extracts prepared for LC-ESIMS/MS analysis was studied at varying cold temperatures (4, -20, and -76 degrees C). Storage of milk samples at 4 degrees C resulted in measurable losses of all beta-lactams after 6 days (>50% in most cases). Slow degradation of penicillin G, cloxacillin, and oxacillin was observed in milk stored at -20 degrees C, but no losses were recorded at -76 degrees C over 4 weeks. All antibiotics showed good stability at all temperature tested in milk extracts prepared for LC-ESIMS/MS analysis. The results of this study emphasize adherence to adequate sample handling and storage protocols as to reflect residue levels at the time of sample submission.
authors.affiliation: Department of Quality & Safety Assurance, Nestlé Research Center, Nestec Ltd, Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland.
authors.forename: Sonja
authors.initials: S
authors.lastname: Riediker
authors.forename: Andreas
authors.initials: A
authors.lastname: Rytz
authors.forename: Richard H
authors.initials: RH
authors.lastname: Stadler
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis*; D002417:Cattle; D002853:Chromatography, Liquid / Q000379:methods*; D003080:Cold Temperature; D007769:Lactams / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000900:Anti-Bacterial Agents; D007769:Lactams