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Observed Concentration (ng/g)Observed Concentration (ng/g)Observed Concentration (ng/g)Evaluation of immunoassay kits for determination of ochratoxin A in cereals4.2.3 Matrix effectExtracts of wheat, winter barley and oats were prepared according to the recommendations of Charm. Twocalibration curves were constructed: one in the undiluted matrix and one in the 5 times diluted matrix using Charmproprietary dilution buffer. When the calibration curves are examined visually (Figure 9, Figure 10, and Figure 11) it‟simmediately clear there is no evident influence of the matrix.302520151050ControlWheat UndilutedWheat dilutedWheat0 5 10 15 20 25Actual Concentration (ng/g)Figure 9: Standard curves of ochratoxin A (ng/g) in wheatversus control (proprietary buffer)35302520151050ControlWinter barleyBarley UndilutedWheat diluted0 5 10 15 20 25Actual Concentration (ng/g)Figure 10: Standard curves of ochratoxin A (ng/g) in winterbarley versus control (proprietary buffer)35302520151050ControlOat UndilutedOat DilutedOats0 5 10 15 20 25Actual Concentration (ng/g)Figure 11: Standard curves of ochratoxin A (ng/g) in oatsversus control (proprietary buffer)The results in Table 46 confirm this: Lin‟s concordance coefficient (ρ c) indicates there is no statistical differencebetween any of the calibration curves in the matrix (diluted or undiluted). Comparing the LOD/LOQ reveals nosignificant increase in variability.Table 46: Matrix effectContolWheatUndilutedWheatDilutedBarleyUndilutedBarleyDilutedOatsUndilutedOatsDilutedSLOPE 0.66 0.60 0.61 0.66 0.73 0.64 0.71INTERCEPT -0.02 0.12 0.36 0.10 -0.29 -0.14 -0.31R 2 0.98 0.97 0.96 0.98 0.97 0.97 0.98CR% 100.0 90.27 92.97 99.46 110.27 96.76 108.11ρc 1.00 0.98 0.98 0.98 0.97 0.98 0.99LOD (ng/g) 1.42 1.62 2.14 1.41 1.61 1.60 1.32LOQ (ng/g) 4.31 4.90 6.48 4.28 4.89 4.86 3.994-48 Experimental evaluation | CODA-CERVA