Identification of Nitrofuran Metabolites

Because nitrofuran metabolites are very small molecules, the marker metabolites are not highly specific. This is especially the case for SEM. However, the presence of tissue-bound metabolites is more specific, because this indicates the administration of nitrofurans. Therefore, analytical methods are described focusing on bound residues.  

Prior to acidic hydrolysis, the samples are extracted several times with water, methanol, and/or ethyl acetate to remove unbound residues. After removal of excessive organic solvent, samples are hydrolyzed and treated according to standard procedures, resulting in the detection of bound nitrofuran metabolites only. 

An example of the low selectivity of SEM as a marker metabolite for nitrofurazone is the false non-compliant findings caused by the use of azodicarbonamide (ADC, 

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Nitrofurans are banned substances within the EU and in some other countries because of their mutagenic and geno-toxic characteristics. Nitrofuran metabolites are still found, primarily in aquaculture products originating from Southeast Asia, with SEM (the metabolite of nitrofurazone) having the highest incidence. Methods for detecting residues of nitrofurans aim for protein-bound metabolites that may persist in tissues for considerable periods after treatment. Methods are reported for the detection and identification of nitrofuran metabolites in many different food products. The main difficulty in nitrofuran metabolite analysis is the low selectivity of SEM as a marker metabolite of nitrofurazone. Several other possible sources of SEM have been identified and investigated, the most important of which is the use of... 

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