Basic Research on Developing Scallop Tissue Reference Material for Quality Assurance of Diarrhetic Shellfish Poisoning (DSP) Mouse Bioassay-Stability of Okadaic Acid (OA)-

Abstract

The preparation of the reference material (RM) for mouse bioassay (MBA) of diarrheic shellfish poisoning (DSP) toxin was attempted. To obtain basic data on the RM, the stability of okadaic acid (OA), which causes DSP, and the method of spiking scallop tissue with OA were examined. Microwave, ultrasonic wave, and UV, which are conventionally used in experiments or may exist in environment, did not affect on the recovery of OA. The recovery rate of OA from thermo treatment at 50-200 °C was examined periodically. Results suggest that temperature has no effect on the recovery rate of OA at temperatures used during conventional analysis and transportation. However, a rapid decrease in recovery was observed during heating at more than 120 °C. In addition, the half-life of OA heated in the range of 120-130 °C was 1 h. OA in acetone solution that was stored in brown vials or dried at the bottom of brown vials was stable during freezing( -35 °C), refrigeration, and storage at room temperature (20 °C) for six months. The titer of OA tested by MBA was stable in stocked samples, but the recovery rate of OA decreased by about 10 % at the HPLC level after 15 months of storage. It was clarified that the recovery rate of OA absorbed in filter paper decreased gradually but the recovery rate of OA was stable under conditions of three-week refrigeration. Samples were distributed to collaborating laboratories and their results of MBA were compared and we did not find any problems on the quality of RM or on the results of MBA quality assurance.