Homogeneity studies of reference materials by solid sampling - AAS and INAA

The necessity to quantify a natural material's homogeneity with respect to its elemental distribution prior to chemical analysis of a given aliquot is emphasised. The instruments and methods which are currently available are described. Additionally, the calculation of element specific, relative homo geneity factors, H-E and the minimum sample mass, M-5%, to achieve 5% preci sion on a 95% confidence level is given. Especially, in the production and certification of certified reference materials (CRMs) this characteristic i nformation should be determined in order to provide the user with additiona l inherent properties of the CRM, to enable more economic use of the expens ive material and to evaluate further systematic bias of the applied analyti cal technique.