A multiresidue approach for the simultaneous quantification of antibiotics in macroalgae by ultra-high performance liquid chromatography-tandem mass spectrometry

•Green macroalgae as a relevant environmental matrix.•Development of a multi-residue UHPLC method for quantification of 38 antibiotics.•Method fully validated according to EU Decision 2002/657/EC.

Together with fish, algae reared in aquaculture systems have gained importance in the last years, for many purposes. Besides their use as biofilters of effluents, macroalgae's rich nutritional profiles have increased their inclusion in human diets but also in animal feeds as sources of fatty acids, especially important for the fish industry. Nonetheless, algae are continuously exposed to environmental contaminants including antibiotics and possess the ability for bioaccumulation of such compounds. Therefore, the present paper describes the development and validation of an ultra-high performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantification of antibiotics in the green macroalgae Ulva lactuca. This multi-residue method enables the determination of 38 compounds distributed between seven classes and was fully validated according to EU Decision 2002/657/EC.