An optimized method for the accurate determination of nitrofurans in chicken meat using isotope dilution-liquid chromatography/mass spectrometry

A method based on isotope dilution-liquid chromatography/tandem mass spectrometry (ID-LC/MS/MS) has been developed as a reference method for the accurate determination of low-level metabolite residues of 4 nitrofuran antibiotics (furazolidone, furaltadone, nitrofurantoin, and nitrofurazone) in meat. A generally adopted method based on the acid-catalyzed release of protein-bound metabolites, their conversion into 2-nitrobenzaldehyde imine-type derivatives, liquid-liquid extraction, and clean-up by solid-phase extraction cartridges was followed but with modification and further optimization for accurate and non-biased measurement results to be used as a definitive reference method. One isotope-labelled analogue for each of the 4 metabolites was used as an internal standard. Validation and performance characterization of the method were conducted by analyzing gravimetrically fortified chicken meat in the range of 0.5-3 μg/kg. The method provided accurate analytical results with the relative expanded uncertainty of 3%. Thus, the method can be used for providing reliable higher-order reference values for the quality control of analytical methods used in general testing laboratories near and below the minimum required performance limit (MRPL) set at 1 μg/kg by the EU.