Comparison of instrumental neutron activation analysis of geological materials with other multielement techniques

Results obtained for 12 elements in approximately 1600 rocks by instrumental neutron activation analysis (INAA) are compared with those obtained by ICP emission spectrometry (ICP-ES), XRF, and atomic-absorption spectrometry (AAS). Sample duplicates and two controls are used to evaluate the precison of the methods investigated. Application of a method (Maximum Likelihood Functional Relationship) to determine and quantify rotational and translational bias is demonstrated. The elements Na, Fe, Ba, Co, Cr, La, Ni and Rb can be determined in rocks by INAA with sufficient sensitivity and precision, whereas the determination of Ag, Yb, Zn and Zr suffers from inadequate sensitivity. Good agreement is seen in the results for Na (by INAA, ICP-ES and XRF) and AG (INAA and AAS). A significant positive bias (13% or less) is evident in the comparison of results by INAA and ICP-ES or XRF for Cr, Ba, Ni and Fe over a wide range of concentration. A similar trend, though less significant, is observed for the elements Yb, Rb, La and Co; the upper limit of concentration for satisfactory determination is within a decade of the highest detection limit for these elements. Rotational and translational bias is evident for Zn in the comparison of data obtained by INAA and ICP-ES, the results by INAA being appreciably lower above about 400 ppm Zn.