The NIMROC samples as reference materials for neutron activation analysis

The NIMROC reference materials NIM-D, NIM-G, NIM-L, NIM-N, NIM-P, and NIM-S and the precious metal ore PTO-1 have been analysed using thermal and epithermal methods of instrumental neutron activation. The abundances of 40 major, minor and trace elements are reported. The usefulness of the NIMROC reference materials is assessed in terms of the requirements of neutron activation techniques. Of the seven reference materials, NIM-L is the most useful geochemical material for activation analysis. It contains suitably high concentrations of most elements that can be determined. Inhomogeneity problems encountered in PTO-1 for some elements give emphasis to the difficulty of selecting suitable geological material for ultra-trace elements where small quantities of sample are used.