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A liquid chromatography–tandem mass spectrometry confirmatory assay for the simultaneous determination of several tetracyclines in milk considering keto–enol tautomerism and epimerization phenomena

2009; Elsevier BV; Volume: 656; Issue: 1-2 Linguagem: Inglês

10.1016/j.aca.2009.10.012

1873-4324

Bernardete Ferraz Spisso, Marcus Antônio Gonçalves de Araújo Júnior, Mychelle Alves Monteiro, Adélia Mara Belém Lima, Mararlene Ulberg Pereira, Robson Alves Luiz, Armi Wanderley da Nóbrega,

Biosensors and Analytical Detection

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 μg L−1. The validation was performed following the criteria established by Commission Decision 2002/657/EC.