Table 1.

Mean analytical results for 48 analytes in 7 plant CRMs in ng g⁻¹. Total combined uncertainties U, combining measurement uncertainty and variability between replicates, are given with a coverage factor of 2 (k = 2). Results below the limit of detection (quantification) are indicated with  < x_L (< x_Q). Colours give an indication about closeness of agreement with the certified reference value, where available, by measure of the E_n numbers. Green: ∣E_n∣ < 1; yellow: 1 < ∣E_n∣ < 2; red: ∣E_n∣ > 2