Abstract
Dinophysistoxin-2 (DTX-2), an isomer of okadaic acid (OA), recently has been found in Irish waters. DTX-2 was the predominant toxin during prolonged infestations in cultivated mussels along the southwest coast of Ireland. Substantial variations in toxin levels may exist both horizontally and vertically in the water column. The need to take multiple samples and the ethical concern about the use of mammals for routine quality control of shellfish prompted examination of 2 commercially available enzyme-linked immunosorbent assay (ELISA) methods, designed to detect OA, for determination of both OA and DTX-2. One ELISA method (DSPCheck, Sceti Co. Ltd., (Tokyo, Japan) showed good cross-reactivity (40 ± 5%) with standard DTX-2. This study showed that both ELISA methods show good correlation with the liquid chromatographic analysis of 9-anthryldiazomethane derivatives when OA is the predominant toxin present. The sensitivity was also good for OA determination using both methods, which allowed toxin measurement at 10 ng/mL (0.5 ng/well). This level is equivalent to 0.03 μg/g mussel meat. Blank mussel samples spiked with DTX-2 standards gave a good linear correlation (r = 0.997) with this ELISA method when toxin levels were 0.03-0.3 μg/g mussel meat. This range is appropriate for regulatory control of diarrhetic shellfish poisoning.
Development and optimization of an indirect enzyme-linked immunosorbent assay for the determination of Hexoestrol
