Development of a method based on Instrumental Neutron Activation to determine the homogeneity of trace contaminants in pure substances

Abstract

The characterization of the highly pure materials used to realize the primary standards in analytical chemistry is important to evaluate correctly the contribution to the measurement uncertainty due to the calibration. In particular, the information concerning the homogeneity of the materials is essential in order to minimize the effect due to sub-sampling. In this framework we developed a method based on neutron activation to estimate the ratio between the fractions of a contaminant element in two samples. The target uncertainty was fixed to 1%. The preliminary results quantified variations of Na, Sc, Nb, Cr, Cs, Zr, Co, Zn, W and Ir in Mg, Mo, Al and Rh. The results concerning Nb in Mo reached the target uncertainty. The uncertainty achieved for the remaining contaminant elements ranged between 3% and 10%