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

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 W-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 mu g kg(-1) for nitrofurazone and furazolidone and 5.0 mu g kg(-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 C-18 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 mu g kg(-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. (C) 1997 Elsevier Science B.V.