Metals   Plant CRM IPE682 Soil Certified reference material Reference value, mg/kg Measured Value, mg/kg           n=9 % Recovery t-test CRM Reference value, mg/kg Measured Value, mg/ kg           n=6 % Recovery t-test Mean Stddev Mean Stddev Value Stddev Mean Stddev Cu 2.2 0.706 2.15 0.22 97.7 0.070 GBM908-2 56 5 53.7 5.42 95.9 0.421 Zn 10.5 2.06 10.43 1.72 99.3 0.033 GBM908-2 70 24 63.44 15.16 90.6 0.265 Pb 6.77 0.874 7.12 0.89 105.2 0.379 GBM908-2 18 7 16.2 7.54 90.0 0.235 Ni 0.32 0.123 0.36 0.04 112.5 0.323 GBM908-2 26 8 23.7 1.49 91.2 0.287 Co 0.06 0.013 0.07 0.01 116.7 0.745 GBM908-2 21 7 19.6 1.43 93.3 0.199 Mn 21.5 2.27 24.77 3.29 115.2 1.297 Spiking 700 nr 721.4 9.96 103.1 nc Fe 114 17 132.6 17.5 116.3 1.035 G310-10 4.88 nr 4.75 0.64 97.3 nc Cr 0.62 0.153 0.59 0.06 95.2 0.194 G310-10 96 nr 87.5 15.4 91.1 nc Cd 0.32 0.028 0.33 0.04 103.1 0.322 G310-10 5 nr 4.76 1.47 95.2 nc

Table 2: Validation of the analytical method using plant and soil certified reference materials (mg/kg dry wt.), nr refers to CRM standard deviation not reported and nc refers t-test not calculated.