NAA study on homogeneity of reference materials and their suitability for microanalytical techniques

Homogeneity of the existing (Virginia Tobacco Leaves CTA-VTL-2 (ICHTJ), Apa tite Concentrate CTA-AC-1 (ICHTJ), Fine Fly Ash CTA-FFA-1 (ICHTJ)) and cand idate certified reference materials (CRMs) (IAEA-338 Lichen, IAEA-413 Algae , Spruce Shoots RMF II (Germany)) was studied by neutron activation analysi s (NAA). Several samples of small mass ( ca. 1 or 10 mg) taken from various containers were analyzed by instrumental NM and the results for several el ements were compared by Fishers's test and t-test with analogous series of results for samples taken from one container. In the second approach, sampl ing variance was estimated for some elements from overall variance and the components of analytical variance. The results were interpreted with the ai d of Ingamells' sampling constant. Particle size distribution of the refere nce materials was also measured by several techniques. In addition quantita tive determinations for some elements were performed and results compared w ith the certified values. The results of the present study were discussed w ith reference to suitability of CRMs to microanalytical techniques. It was pointed out that the term "microanalysis" itself is not always unequivocall y understood and used.