Fish can potentially accumulate large amounts of cyanotoxins as toxic cyanobacterial blooms are commonly observed in aquatic ecosystems. Moreover, fish consumption has thus the potential to be a human health risk. Suitable and sufficiently robust analytical methods are required to quantify cyanotoxins in a plethora of different fish species. While reporting quantified cyanotoxins in multiple fish species, most studies do not take into account the potential differences of matrix for quantification in fish species during their validation. This study therefore aimed to optimize and validate an UHPLC-MS/MS method for the quantification of eight microcystin congeners and nodularin in the muscles tissue of five different fish species and cod liver. Moreover, the method was applied on multiple fish samples collected from Belgian waters.
Extensive optimizations of the extraction protocol compared to already published methods were necessary before validation of the method was possible. Moreover, elution gradients and the selection of the daughter ions had to be optimized to deal with the matrix effect propagated by the muscle tissues of different fish species.
Eventually, the validation of the method was achieved for the muscle tissue of all fish species and cod liver. A limit of quantification (LOQ) of 5 µg kg-1 was achieved for MC-LY, MC-LR and MC-LF, while for the five MCs and NOD an LOQ of 10 µg kg-1 was found.
Multiple microcystin congeners were detected in the liver of perch and sander, up to 88.3 µg/kg sum of analyzed microcystins. Moreover, 6 µg/kg of MC-LR was found in perch muscle tissue, while MC-RR was also detected.
