What does the minimum sample intake mean?
The value stated on the certificate refers to the average analyte content of one unit of a reference material. All reference materials (with the exception of homogeneous solutions and gases) are intrinsically heterogeneous but sufficiently large sample intakes eliminate the effect of this heterogeneity. The minimum sample intake is the minimum amount of material that is still representative for the average of the bottle. If the sample intake is less, differences between the analytical portions significantly influence the variability of the results. Therefore, producers cannot guarantee the certified value for individual subsamples if these subsamples are smaller than the minimum sample intake stated on the certificate.