Determination of nitrofuran metabolite residues in eggs by liquid chromatography-mass spectrometry

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the determination of metabolites of furazolidone, furaltadone, nitrofurantoin, and nitrofurazone in eggs. The procedure requires an acid-catalysed release of protein-bound metabolites, followed by their in situ conversion into the 2- nitrobenzaldehyde (NBA) derivatives. The sample cleanup was performed on a solid phase extraction (SPE) cartridge. LC- MS/MS analysis was performed by positive electrospray ionisation (ESI) applying multiple reaction monitoring (MRM) of two transition reactions for each compound. The validation of the method was conducted following the European Union criteria for the analysis of veterinary drug residues in foods. The decision limits (CCα) were 0.16-0.24 µg/kg, and the detection capabilities (CCβ) 0.22-0.36 µg/ kg.