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Evaluation of immunoassay kits for determination of ochratoxin A in cereals4.2.4 AccuracyTo assess the accuracy of the kit two reference materials were analyzed. The results, calculated according to themethod described in ref 73 . are summarized in Table 47.Table 47: Accuracy on two reference materialsFAPAS BIPEATRUE VAL(ng/g)4.13 13.25N 5.00 9.00DF 4.00 8.00t (95) 2.78 2.31SD (ng/g) 0.55 2.28Q1 (ng/g) 3.00 9.00Q3 (ng/g) 4.00 12.00Mean (ng/g) 3.40 10.56xe-xt (ng/g) -0.73 -2.69Criterion (ng/g) 0.68 1.76From these results it is clear that both materials are biased slightly negatively in a statistical significant manner.4.2.5 Blank sample analysisTo assess the LOD of the kit another method using the analysis of blank samples (wheat, winter barley and oats) wasused.Blank matrices were extracted 3 times on 3 different days. These data were pooled and used to calculate the LODaccording to the protocol described in 4.1.4.5.2. and are summarized in Table 48.Table 48: Minimum detectable limitWheat Winter barley OatsMean (ng/g) 0.11 0.67 0.33N 9.00 9.00 9.00Degrees freedom 8.00 8.00 8.00t (95%) 2.31 2.31 2.31SD (ng/g) 0.33 0.50 0.73Q1 (ng/g) 0.00 0.00 0.00Q3 (ng/g) 0.00 1.00 0.00∆xmin (ng/g) 0.81 1.22 1.77Detection limit (ng/g) 0.92 1.88 2.21These LOD‟s agree well to the data obtained in 4.2.2 or those reported by Charm (LOD≈ 1 ng/g).CODA-CERVA | Experimental evaluation 4-49