We developed and validated a method for the extraction, identification, and quantitation of four nitrofuran metabolites, 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), semicarbazide (SC), and 1-aminohydantoin (AHD), as well as chloramphenicol and florfenicol in a variety of seafood commodities. Samples were extracted by liquid-liquid extraction techniques, analyzed by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), and quantitated using commercially sourced, derivatized nitrofuran metabolites, with their isotopically labeled internal standards in-solvent. We obtained recoveries of 90-100% at various fortification levels. The limit of detection (LOD) was set at 0.25 ng/g for AMOZ and AOZ, 1 ng/g for AHD and SC, and 0.1 ng/g for the phenicols. Various extraction methods, standard stability, derivatization efficiency, and improvements to conventional quantitation techniques were also investigated. We successfully applied this method to the identification and quantitation of nitrofuran metabolites and phenicols in 102 imported seafood products. Our results revealed that four of the samples contained residues from banned veterinary drugs.
Keywords: UHPLC−MS/MS; chloramphenicol; florfenicol; liquid/liquid extraction; metabolites; method development; nitrofurans; validation.