Determination of OA-toxins by a phosphatase inhibition assay. Collaborative study.

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Just published the collaborative study on OkaTest, colorimetric phophatase inhibition assay for OA-toxins. Smienk et al, 2013, J. AOAC International. 96, 1, 77-85. Smienk.et al.2013, JAOAC, 96,1,77-85 Abstract A collaborative study to validate a colorimetric phosphatase inhibition assay for quantitative determination of the okadaic acid (OA) toxins group in molluscs, OkaTest, was conducted. Eight test materials including mussels, scallops, clams and cockles were analysed as blind duplicates. Blank samples and materials containing different OA-toxin levels ranging from 98 to 275 µg/kg OA equivalents were included. The study was carried out by a total of 16 laboratories from 11 different countries. Values obtained for repeatability relative standard deviations (RSDr) ranged from 5.4% to 11.2% (mean 7.5%). Reproducibility relative standard deviation (RSDR) values were between 7.6% and 13.2% (mean 9.9%). The HORRAT values ranged between 0.4 and 0.6. A recovery assay was also carried out using a sample spiked with OA. A mean recovery of 98.0% and a relative standard deviation of 14.5% were obtained. The results obtained in this validation study indicate that the colorimetric phosphatase inhibition assay, OkaTest, is suitable for the quantitative determination of the OA-toxins group. OkaTest could be used as a complementary test to the reference method for monitoring the OA-toxin group. Details of the test materials, number of results submitted and results after removing outliers, together with performance values of precision (repeatability and reproducibility) obtained for the colorimetric OkaTest. Sr: Repeatability standard deviation. SR: Reproducibility standard deviation. RSDr: Repeatability relative standard deviation. RSDR: Reproducibility relative standard deviation.  r: Repeatability Limit, R: Reproducibility Limit.