Abstract:As the most stable metabolite of nitrofurazone (NFZ), semicarbazide (SEM) can be determined after the administration of NFZ in aquatic animals within a few hours. Because of extensive tissue distribution and a long residual period, SEM is used as the exclusive marker for NFZ. However, SEM is naturally present in the shells of crustaceans, such as crayfish, shrimp, prawns, and soft-shell crabs. To avoid false-positive results induced by SEM alone and to precisely identify the illegal use of NFZ, further investigations on the distribution characteristics of SEM in crustaceans is essential. In the present study, samples of shell, muscle, muscle epidermis, internal organs, and compound eye were collected from Macrobrachium rosenbergii shrimp farms that were not exposed to nitrofural, and SEM was determined in order to investigate the background concentrations in different tissues of the commercial shrimp. Samples were evaluated in accordance with Announcement No.783-1-2006 of the Ministry of Agriculture of the People’s Republic of China. As multiple tissue samples, including compound eye, outer shell, limbs, feet, intestine, gill, muscle epidermis, liver, gonad, and muscle were assessed, the method was suitable for monitoring the background concentration of SEM in different tissues of M. rosenbergii. The average concentration of SEM across all tissues was (12.90±2.47) μg/kg. The average concentrations of SEM in compound eyes, shells, and limbs were (33.29±3.06), (29.00±5.67), and (28.10±7.08) μg/kg, respectively. The lowest concentration of SEM was found in muscle samples, with an average value of (1.83±0.24) μg/kg. The concentration of SEM in commercial M. rosenbergii tissues could be ordered as compound eye > outer shell > limbs and feet > intestine > gill > muscle epidermis > liver > gonad > muscle. Considering that it was difficult to distinguish the source of SEM in M. rosenbergii, the background concentration of SEM should be deducted when determining NFZ residues in this species.
