Identification of endogenous and exogenous semicarbazide (SEM) in crustacea aquatic products using compound-specific nitrogen stable isotope ratio analysis (NSIRA)

Endogenous SEM (SEM end ) naturally occurs in crustacea aquatic products, it confuses the legal verdict of exogenous SEM (SEM ex ) degraded by antibiotic nitrofurazone abuse. In the present study, compound-specific gas phase chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) analysis coupled with a two-step pre-column derivatization was developed for determining the nitrogen stable ratio (δ 15 N) of SEM in shrimp and crab. The optimal derivatization and solid phase extraction (SPE) condition of SEM were screened by Plackett-Burman design and central composite design (CCD) experiment. The nitrogen isotope ratio analysis (NSIRA) of SEM in two types of crustaceans proved that its δ 15 N values significantly decreased from 7.0‰ to 2.0‰ once nitrofurazone being used. Analytical results found that the δ 15 N value of SEM ex in vivo was consistent its nitrofurazone precursor but the value of SEM end was dependent on N-containing components (e.g., tissue protein), ANOVA showed significant difference between two types of SEM (p < 0.05). Based on the δ 15 N variations between SEM itself and its nitrofurazone precursor, tissue protein of crustaceans, the percentages of SEM ex and SEM end can be calculated for its source apportionment in vivo. The limit of detection of SEM is down to 0.21 μg kg −1 and 0.54 μg kg −1 , and the identification lower limit of SEM ex are accurate at 6.27% and 0% for two types of crustaceans. The strategy first realized the independent determination of SEM ex and SEM end in crustacea aquatic products, which explained that high-level SEM in crustaceans can’t as the legal verdict of nitrofurazone abuse in aquaculture.