Agilent Technologies Inc.today announced development of a routine, highly sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method to simultaneously determine four nitrofuran metabolites in food animal tissue. For chicken tissue analysis, the limit of detection for each metabolite ranged from 0.02 to 0.06 ng/mL.
Food safety officials can use this technique to accurately screen imported foods for the presence of nitrofurans, which pose a risk to public health because of their known carcinogenicity. For food product exporters, this method provides a routine and reliable means of ensuring that their exports meet inspection requirements prior to shipment, reducing the potential loss from rejected shipments.
The nitrofuran antibacterial drugs (furazolidone, furaltadone, nitrofurazone and nitrofurantoin) are widely used as feed additives to prevent bacterial enteritis in cattle, fish, swine and poultry, yet the presence of nitrofuran residues in edible tissue is a major human health concern. The use of nitrofurans in food animal production was banned in the European Union in 1995 and in the United States in 2002.
In addition to the public health implications, the presence of nitrofuran residues in food can have significant economic consequences for worldwide food product importers and exporters. In early 2002, the EU tightened its inspection policy for food imports after nitrofuran residues were found in shrimp, fish and poultry imports. The inspections not only reduced the volume of those imports entering the EU, but also lowered the confidence of consumers in the safety of imported food.
The analysis of nitrofurans is complicated by their rapid metabolism, as the drugs have in vivo half-lives of less than a few hours. Detecting the parent drug in animal tissue, therefore, is not practical. However, tissue-bound metabolites of these antibacterial drugs are detectable for several weeks. It is possible to release these metabolites under moderately acidic conditions and derivatize them for analysis using LC and ultraviolet detection, using MS for confirmation.
Agilent chemists applied this method to the analysis of nitrofurans in chicken muscle and liver tissues. They performed the analysis using an Agilent 1100 Series LC/MSD system with electrospray ionization. Sample cleanup and analyte enrichment were performed using liquid-liquid extraction with ethyl acetate, followed by solvent wash, acid extraction by homogenization, and derivatization using 2-nitrobenzaldehyde. Each metabolite produced a simple mass spectrum containing a strong signal corresponding to [M+H]+. The analysis provided excellent linearity with correlation coefficients greater than 0.999 for all metabolites and very low limits of detection, from 0.02 to 0.06 ng/mL.
Further information is available by requesting Agilent application note "Determination of the Metabolites of Nitrofuran Antibacterial Drugs in Chicken Tissue by Liquid Chromatograph-Electrospray Ionization-Mass Spectrometry (LC-ESI-MS)," Agilent publication number 5988-8903EN.