J. Prokisch et al., Estimation of the minimum uncertainty of DNA concentration in a genetically modified maize sample candidate certified reference material, FRESEN J AN, 370(7), 2001, pp. 935-939
Homogeneity testing and the determination of minimum sample mass are an imp
ortant part of the certification of reference materials. The smallest theor
etically achievable uncertainty of certified concentration values is limite
d by the concentration distribution of analyte in the different particle si
ze fractions of powdered biological samples. This might be of special impor
tance if the reference material is prepared by dry mixing, a dilution techn
ique which is used for the production of the new and third generation of ge
netically modified (GMO) plant certified reference materials. For the produ
ction of dry mixed PMON 810 maize reference material a computer program was
developed to calculate the theoretically smallest uncertainty for a select
ed sample intake. This model was used to compare three differently milled m
aize samples, and the effect of dilution on the uncertainty of the DNA cont
ent of GMO maize was estimated as well. In the case of a 50-mg sample mass
the lowest achievable standard deviation was 2% for the sample containing 0
.1% GMO and the minimum deviation was less than 0.5% for the sample contain
ing 5% GMO.