Screening and confirmation of chloramphenicol in shrimp tissue using ELISA in combination with GC-MS2 and LC-MS2

Abstract According to the European Commission Decision 2001/699/EC and 2001/705/EC certain fishery and aquaculture products, imported from China, Vietnam or Indonesia and intended for human consumption, must be subjected to a test in order to ensure the absence of chloramphenicol residues. For that reason an analytical method has been developed and validated based on ELISA for screening and gas chromatography–tandem mass spectrometry (GC–MS 2 ) or liquid chromatography–tandem mass spectrometry (LC–MS 2 ) for confirmation. The chloramphenicol ELISA was carried out directly on an aqueous extract of the shrimps or after an extraction with ethyl acetate. Confirmation of suspect samples was performed after extraction with ethyl acetate and defatting with n -hexane. The clean-up was based on solid phase extraction using C 18 cartridges or reversed phase HPLC. After derivatisation with N -methyl- N -(trimethylsilyl)trifluoroacetamide (MSTFA), the final extracts were analysed by GC–MS 2 in the negative ion chemical ionisation mode. Confirmation of chloramphenicol was also possible with LC–MS 2 after the same clean-up. Both selective techniques made it possible to detect chloramphenicol residues at the 0.1 μg kg −1 level starting from 20 g of matrix for enzyme-linked immunosorbent assay (ELISA) with organic solvent extraction, or from 5 g of matrix for ELISA with aqueous extraction.