Isolation of bound residues of nitrofuran drugs from tissue by solid-phase extraction with determination by liquid chromatography with UV and tandem mass spectrometric detection

Use of nitrofuran drugs in food-producing animals has been prohibited within the EU because they may represent a public health risk. Monitoring compliance with the ban has focused on the detection of protein-bound nitrofuran metabolites which, in contrast to the parent compounds, are stable and persist in animal tissues. This paper describes a solid phase extraction clean-up procedure for the protein-bound metabolite of furazolidone, 3-amino-2-oxazolidone (AOZ), allowing detection of the derivatised metabolite, NPAOZ, at residue level. Validation studies for the method on porcine liver samples fortified at 5 and 25 ng g −1 show mean recovery of 84±19.2 and 90±16.3%, respectively. Comparison between liquid chromatography with UV or tandem mass spectrometric detection shows agreement within 10% for incurred porcine liver samples.