A relatively rapid protein phosphatase-based assay was developed for detecting okadaic acid in extracts of shellfish, using oysters (Crassostrea virginica) as a model, The assay has good sensitivity detecting okadaic acid in crude methanolic extracts of oysters at greater than or equal to 4 ng/ml (greater than or equal to 0.1 ng/assay). Assay accuracy for detecting toxic shellfish was validated through a series of spike recovery experiments, In more than 320 assessments, all oysters containing toxic amounts of okadaic acid (greater than or equal to 0.2 mu g/g) were detected, Results of analysis of the same extract by phosphatase assay and liquid chromatography gave very high correlation.
