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  • 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.
    Author: Spisso BF, de Araújo MA, Monteiro MA, Lima AM, Pereira MU, Luiz RA, da Nóbrega AW.
    Journal: Anal Chim Acta; 2009 Dec 10; 656(1-2):72-84. PubMed ID: 19932817.
    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.
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