Enhancing the Detection of Cyclic Imines in Marine Mollusks Using Advanced LC/MRM-MS

Recent significant changes in the marine ecosystems have led to an increased occurrence and exposure of a novel marine biotoxin group known as cyclic imines (CIs). To mitigate associated risks, rapid and sensitive monitoring platforms for detecting CIs in marine organisms are essential. Although liquid chromatography coupled with mass spectrometry (LC/MS) is a promising tool for managing hazardous substances, characterizing CIs is challenging due to difficulties in distinguishing trace amounts from the complex matrix of substances derived from marine organisms. Therefore, a critically improved method that can accurately and rapidly detect various types of CIs, while minimizing interference effects, is needed. In this study, we investigated optimal purification conditions to enhance the reliability in LC/MRM-MS analyses for CIs. Specifically, we spiked three types of seven CIs (PnTX E, PnTX F, PnTX G, 13-des-SPX C, 13,19-dides-SPX C, 20-des-SPX G, and GYM A) into a shellfish matrix and assessed the effectiveness of two purification methods. The hydrophilic–lipophilic balanced solid-phase extraction (HLB-SPE) with methanol condition provided the best results in LC/MRM-MS analysis of all seven CIs. The recoveries of validated CIs ranged from 80 to 120% at three points encompassing 2, 10, and 100 times the limit of quantitation (LOQ) on the quantitation curve, respectively. The effectiveness of our enhanced CI quantitative platform was demonstrated through the monitoring of shellfish collected from the Korean Waters. Ultimately, our findings provide a valuable reference for enhancing quantitative accuracy of LC/MS-based CI monitoring.