Overcoming Analytical Challenges for the Detection of 27 Cyanopeptides Using a UHPLC-QqQ-MS Method in Fish Tissues

The increasing occurrence of harmful cyanobacterial blooms in freshwater ecosystems poses important risks to aquatic organisms and human health due to the production of bioactive secondary metabolites such as cyanopeptides. While analytical methods for microcystins are well developed, there is a notable lack of validated protocols for the broader spectrum of cyanopeptides in biota. This study presents the development and validation of a robust UHPLC-QqQ-MS method for the simultaneous extraction, cleanup, and quantification of 27 cyanopeptides, including microcystins, anabaenopeptins, microginins, aeruginosins, aeruginoguanidine, and nodularin, in fish muscle, liver, and whole fish tissues. Comprehensive optimization was conducted to minimize matrix effects and analyte losses during every step of sample preparation. The method demonstrated generally high recoveries (28-98%), good precision (RSD < 20%), and sensitivity, with MQLs below 0.5 ng g^-1 for most analytes. Microginins posed analytical challenges due to their amphiphilic structure, which contributed to significant losses during filtration and extraction; the reasoning is discussed. Application to wild fish collected after a mass mortality event revealed no detectable cyanopeptide contamination but confirmed the method's suitability for comprehensive detection. This represents an important advancement in cyanopeptide analysis, offering a valuable tool for environmental risk assessment and food safety evaluation related to harmful cyanobacteria.