Identification and Quantitative Analysis of Unusual Unsaturated Fatty Acid Isomers in Fresh and Dry Marine Invertebrates by Covalent Adduct Chemical Ionization Mass Spectrometry

Edible marine invertebrates are good sources of omega-3 polyunsaturated fatty acids (PUFA). However, these organisms display complex FA profiles with monounsaturated FA featuring unusual double-bond positions and PUFA containing polymethylene-interrupted configurations. Identifying and quantifying these isomers pose major analytical challenges, particularly when coelution occurs. Covalent adduct chemical ionization mass spectrometry enables de novo identification of unusual PUFA and sensitive quantification of trace and coeluted FA due to its high specificity. In this study, we developed a straightforward method for quantifying coeluted polymethylene-interrupted PUFA without standards or specialized columns and analyzed the FA compositions of three marine invertebrates commonly marketed fresh and dried. A total of 100 FA were identified, including several novel odd-chain monounsaturated FA. Marked interspecies differences were observed for various FA, while drying had a small impact. This work provides new insights into the nutritional values of dry marine invertebrates and introduces a practical approach for PUFA isomer analysis.