Determination of okadaic acid in shellfish by using a novel chemiluminescent enzyme-linked immunosorbent assay method

A direct competitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) was developed to determine okadaic acid (OA). Concentrations of the capture monoclonal anti-OA antibodies, conjugate of OA-HRP and a composition of blocking buffers were varied to optimize the assay condition. The values of IC10, IC50 and working range (IC20-IC 80) for CL-ELISA were 0.01, 0.07, and 0.03-0.2 ng/mL, respectively. Additionally, the analytical recovery values of CL-ELISA from 3 shellfish spiked samples with OA concentrations of 0.03, 0.1 and 0.2 ng/mL ranged from 86.7% to 111.2%. Closely examining the OA concentrations in 19 various shellfish products performed by CL-ELISA revealed that OA concentrations in 6 of the 19 examined samples was undetected, whereas the 13 samples were contaminated with low levels of OA ranging from 1.2 to 8.0 ng/g.