Detection, accumulation and distribution of nitrofuran residues in egg yolk, albumen and shell

Nitrofuran antibiotics have been banned for use in food-producing animals in many countries, including the European Union, owing to the threat they pose to human health. Research continues into the accumulation of these drugs in animal tissues and into the appropriate methods for their detection. In this study, an LC-MS/MS method is presented for the detection of the parent compounds, furazolidone, nitrofurantoin, furaltadone and nitrofurazone, in eggs. The parent compounds are first extracted into ethyl acetate, fats are removed by partition between acetonitrile and hexane, and the concentrated sample is analysed by LC-MS/MS. Decision limits (CCalpha) for the parents were < or =1 microg kg-1 for all four compounds. Within-day and between-day CVs are well within the limits stated in Commission Decision 2002/657/EC. The method provides an alternative to the testing of side-chain metabolites in eggs, which is particularly important in the case of nitrofurazone, where semicarbazide contamination of food has been attributed to sources other than nitrofurazone use. This method was used together with a method for the detection of the side-chain metabolite compounds, 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-1,3-oxazolidin-2-one (AMOZ), 1-amino-hydantoin (AHD) and semicarbazide (SEM), to study the accumulation and distribution of nitrofurans in eggs. Eggs were collected from four groups of hens that had been treated with one of the nitrofurans at a feed concentration of 300 mg kg-1 for 1 week. Parent compounds and metabolites were found in the yolk, albumen and shell. Albumen/yolk ratios for the parent compounds were 0.7, 0.82, 0.83 and 0.31 for furazolidone, furaltadone, nitrofurantoin and nitrofurazone, respectively. Ratios for the side-chain metabolites were 1.02, 1.06, 0.83 and 0.55 for AOZ, AMOZ, AHD and SEM, respectively. However, 50% of the total SEM residues were found in eggshell. This may be significant if eggshell products reach the consumer.