Immunoaffinity extraction as a new approach for an improved liquid chromatography-mass spectrometric or fluorimetric determination of okadaic acid in shellfish and algae Original Research Article

A new immunoaffinity solid-phase extraction sorbent (immunosorbent) has been developed by bonding polyclonal antibodies raised against okadaic acid (OA) onto silica. It has been evaluated for the selective isolation of okadaic acid and related dinophysistoxins in shellfish and algae using LC coupled to fluorescence detection after derivatization with a fluorescent agent or to mass spectrometry (MS). When the derivatization reaction is applied to mussel matrix, many interferences are generated due in part to the sample matrix and in part to reagents instability. Therefore, the clean-up of derivatized extracts using the immunosorbent was optimized as a rapid, simple and solvent-free procedure which met the required detection limit of 1 μg/g hepatopancreas. When the analysis is performed using LC-electrospray-MS, the immunosorbent provided very clean extracts in a single step and it was demonstrated that immunoextraction-LC-MS was the best alternative to current procedures. The reliability of the immunoclean-up procedures applied to okadaic acid was demonstrated using certified mussel reference material, as well as using algae samples.