title: A liquid chromatography-tandem mass spectrometry confirmatory assay for the simultaneous determination of several tetracyclines in milk considering keto-enol tautomerism and epimerization phenomena.
abstract: A liquid chromatography-electrospray ionization tandem mass spectrometric (LC-ESI-MS/MS) method for the analysis of several tetracyclines residues in bovine milk has been developed. Milk deproteinization/extraction of samples was performed with acidified acetonitrile. After diluting and purification by solid-phase extraction (SPE), the extracts were injected into the instrument operated in Multiple Reaction Monitoring (MRM) acquisition mode. The reversible epimerization at C-4 of oxytetracycline, tetracycline and chlortetracycline and the keto-enol tautomerism of chlortetracycline between C-11a and C-12 were considered for reliable quantification. Degradation was also taken in account and minimized for the same purpose. A central composite (response surface) design with desirability function was employed for the optimization of extraction and clean-up steps. The optimization improved the extraction efficiency of the more polar analytes reaching 93.9% for 4-epioxytetracycline and 95.8% for oxytetracycline at 100 microg L(-1). The validation was performed following the criteria established by Commission Decision 2002/657/EC.
authors.affiliation: National Institute for Quality Control in Health/Oswaldo Cruz Foundation (INCQS/FIOCRUZ), Av. Brasil 4365, Rio de Janeiro, RJ, Brazil. bernardete.spisso@incqs.fiocruz.br
authors.forename: Bernardete Ferraz
authors.initials: BF
authors.lastname: Spisso
authors.forename: Marcus Antônio Gonçalves
authors.initials: MA
authors.lastname: de Araújo
authors.forename: Mychelle Alves
authors.initials: MA
authors.lastname: Monteiro
authors.forename: Adélia Mara Belém
authors.initials: AM
authors.lastname: Lima
authors.forename: Mararlene Ulberg
authors.initials: MU
authors.lastname: Pereira
authors.forename: Robson Alves
authors.initials: RA
authors.lastname: Luiz
authors.forename: Armi Wanderley
authors.initials: AW
authors.lastname: da Nóbrega
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D008968:Molecular Conformation; D052616:Solid Phase Extraction; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013754:Tetracyclines / Q000032:analysis* / Q000737:chemistry*
chemical_list: D013754:Tetracyclines