Determination of nitrofuran residues in avian eggs by liquid chromatography–UV photodiode array detection and confirmation by liquid chromatography–ionspray mass spectrometry

Abstract

A high-performance liquid chromatographic–UV–Vis photodiode-array detection (HPLC–DAD) method for the determination of nitrofuran residues, nitrofurazone, furazolidone and furaltadone, in chicken eggs is described. Confirmation of the identity of nitrofurazone, furazolidone and furaltadone was performed by high-performance liquid chromatography–mass spectrometry (HPLC–MS) using an atmospheric pressure ionization (API) source and an ionspray interface. The nitrofuran residues were extracted from eggs with acetonitrile and the extracts purified by liquid–liquid partitioning. Analytes were chromatographed isocratically with an octadecylsilyl (ODS) column and an UV–Vis detector set at 362 nm and identified by comparing the retention times and UV–Vis spectra of the sample peaks with the reference compounds. The HPLC–DAD limit of detection based on a signal-to-noise ratio (S/N) of 3, was estimated to be 2.5 μgkg−1 for nitrofurazone and furazolidone and 5.0 μgkg−1 for furaltadone. The ionspray HPLC–MS was carried out on the purified extracts. The HPLC–MS method involved the separation of analytes on a C18 column with acetonitrile–water (50:50, v/v), containing 1 mM ammonium acetate and 0.025% acetic acid, with selected-ion monitoring (SIM) of only protonated molecules, [M+H]+ of the analytes. The overall average recovery in nitrofuran fortified eggs was 85.3±3.8% for nitrofurazone, 88.1±3.9% for furazolidone and 87.1±3.7% for furaltadone. The HPLC–MS limit of detection, based on a S/N of 3, was estimated to be 3.2, 1.6 and 1.0 μgkg−1 for nitrofurazone, furazolidone and furaltadone, respectively. HPLC–MS has shown itself to be a sensitive, selective and rapid method and was successfully used for the confirmation analysis of nitrofurazone, furazolidone and furaltadone in avian eggs for regulatory purposes.