Determination of total nitrofuran metabolites in shrimp muscle using liquid chromatography/tandem mass spectrometry in the atmospheric pressure chemical ionization mode.

The method of MacMahon and Lohne for analysis of nitrofuran metabolites in shrimp was optimized to streamline the extraction processes and the LC analysis. This revised method includes 16 h of mild acid hydrolysis/derivatization followed by ethyl acetate extraction and analysis by LC/MS/MS in the atmospheric pressure chemical ionization mode. This revised method was validated in shrimp for concentrations of 0.25 to 2.0 ng/g. The LOQ was 0.25 ng/g for all metabolites. The LOD was 0.052 nglg for 1-aminohydantoin (AHD), 0.206 ng/g for 3-amino-2-oxazolidinone (AOZ), 0.108 ng/g for semicarbazide (SC), and 0.062 ng/g for 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ). The spike recoveries with RSD into negative matrix at 1 ng/g were 100.2% (3.2%) for AHD, 102.5% (1.0%) for AOZ, 103.7% (2.3%) for SC, and 104.0% (3.3%) for AMOZ. The spike recoveries at 1 ng/g into unknown samples (n=108) containing varied levels of nitrofuran metabolites were 112.6% (25.7%) for AHD, 108.1% (12.1%) for AOZ, 103.0% (12.0%) for SC, and 100.3% (6.9%) for AMOZ. Interday precision with samples containing incurred AOZ concentrations of 0.92 to 17.8 ppb performed over a year was 10.4% RSD. The method is accurate and precise for determining nitrofuran concentrations in the edible tissue of shrimp.