Accurate Quantification of Okadaic Acid Group Toxins in Bivalves by Simple Solid-Phase Extraction Clean-up Using Hydrophilic-Lipophilic Packing Materials

In Japan, an analytical method based on LC/MS/MS has been introduced as the official analytical method for diarrheal shellfish toxins (okadaic acid (OA), dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2), and their esters) in bivalves. In this study, a simplified method was developed by applying solid phase extraction using hydrophilic-lipophilic packing materials, wherein the saponified bivalve extract loaded into the cartridge was eluted without a cleanup process. In an analysis of a scallop sample, the impact of the matrix effect in LC/MS/MS measurements on the observed analytical results was evaluated by comparing the peak intensities of OA, DTX1, and DTX2 in the processed solution using the present method with those in methanol; the rate of change ranged from -1 to 6 %, and no significant change was observed. Then, the validation parameters (trueness, repeatability, intermediate precision, selectivity, and limits of quantification), for which performance criteria were established by the official analytical method were evaluated, and all observed results met the criteria. The trueness of the method was further evaluated by analyzing a scallop -certified reference material, and analytical results corresponding to the certified values were observed. The bivalve sample was then expanded to include clam, oyster, and mussel samples. The impact of the matrix effect on LC/MS/MS measurements was evaluated as described above, and satisfactory results ranging from -16 to -1 % were observed. The trueness and repeatability were further evaluated, and the results met the individual criteria of the official analytical method. The results obtained in this study indicate that the present method offers highly accurate analytical performance for diarrheal shellfish toxins in bivalves.