Application of non-target analysis and high resolution mass spectrometry for the identification of thermal transformation products of oxytetracycline in pacific white shrimp

Oxytetracycline is an antibiotic authorized for use in aquaculture and is often detected in seafood products, especially shrimp. Previous studies investigating the fate of oxytetracycline in shrimp tissues after cooking were limited to quantification of parent compound residues, and did not describe any potential transformation products formed. Hence, the main objective of this study was to apply a non-target analysis workflow to study the fate of oxytetracycline in shrimp muscle. Furthermore, “water” and “spiked” models were evaluated if they were suitable to track the transformation of OTC in incurred muscle, and determine if the matrix plays a role in the transformation pathway. First, four different extraction methods were compared for the determination of oxytetracycline in muscle. Secondly, raw and cooked samples were then extracted using the suitable method (acidified water/methanol/acetonitrile with clean-up of samples achieved using freezing) and were analyzed by HPLC-QTOF-MS. Oxytetracycline levels were reduced by 75 % and 87% in muscle and water, respectively. Identification of thermal transformation products was limited to formula generation, but results showed that different compounds were identified in spiked and incurred muscle.