Use of standard reference materials in microanalysis

The NBS Standard Reference Material SRM 1633a, Coal Fly Ash, is a suitable primary or secondary trace element standard when used in microanalytical techniques requiring sample weights in the μg-mg range. Except for Ni, Ba, Se, and Tb relative standard deviations of less than 20% are obtained for 24 elements. The USGS BCR-1 Columbia River Basalt also appears to be suitable as a standard in microanalytical techniques, although no certified concentration data are available. Coals, e.g., NBS SRM 1632, are less suitable for such standards because of mineralogical heterogeneity. The RSD(%) values for Ni, Ba, Zr, Sb, and U could be explained as high sampling errors associated with mineralogical species of minor abundances in the coal