Coupling High-Throughput Magnetic-Bead-Based Immunoaffinity with LC–MS/MS Analysis for Quantifying Cylindrospermopsin in Different Fish Tissues

Cylindrospermopsin (CYN) can bioaccumulate in aquatic food chains and cause potential toxicity to human and animal health. When analyzing biological samples using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the presence of complex matrices is a major concern. In this study, we developed a novel immunoaffinity extraction method for CYN enrichment in different biological matrices. Magnetic beads bound with a monoclonal antibody against CYN were used as affinity probes to specifically enrich CYN in samples, which effectively eliminated matrix effects for LC-MS/MS analysis. Under optimized conditions, the automated method processes 32 samples in 54 min without any centrifugation or filtering steps. When coupled to LC-MS/MS, this new method shows excellent sensitivity (LOQ, 0.025 μg L^-1), linearity (R² > 0.99, 0.125-100 μg L^-1), precision (RSD < 6%), and recoveries (85-105%). Using the established method to measure CYN contents in 10 muscle and liver tissue samples of fish from a reservoir of southern China, we found its analogue deoxy-cylindrospermopsin (deoxy-CYN) was detected more frequently and also with higher concentration than CYN. An average concentration of 2.38 μg kg^-1 in muscle and 71.99 μg kg^-1 in liver suggested that CYN accumulation is highly tissue-specific. This is the first report of immunoaffinity extraction for CYN enrichment. Our results demonstrate that the developed method is reliable and offers significant application prospects.