Novel source of semicarbazide: levels of semicarbazide in cooked crayfish samples determined by LC/MS/MS

Nitrofuran antibiotics were previously used in animal healthcare but are now prohibited. Semicarbazide is a breakdown product of 5-nitrofurazone and protein-bound semicarbazide is used as a marker residue for the illegal use of 5-nitrofurazone. However, the presence of the prohibited semicarbazide has been reported in some food items of animal origin. A novel observation is reported that semicarbazide can be detected in Finnish crayfish samples, i.e. crustacea, never medicated with nitrofurazone. The origin of the semicarbazide is presently unknown. Positive identification was undertaken by liquid chromatography coupled with tandem mass spectrometry detection. The level of semicarbazide was determined as the protein-bound form as well as the total amount of semicarbazide in the sample. The average levels of total semicarbazide and the protein-bound form were 4.2 and 0.5 ng g(-1) fresh crayfish meat, respectively. All the tested samples (n = 18) contained traces of semicarbazide, the highest amount being 12 ng g(-1) fresh crayfish meat.