Rare-earth elements in the NBS standard reference materials spinach, orchard leaves, pine needles and bovine liver.

A highly sensitive radiochemical neutron activation method for the determination of all rare-earth elements (REE) in NBS biological reference materials is described. The materials are irradiated, dissolved in HF/HCl solutions, mixed with scandium and REE carriers (except La, Pr, Nd, Dy, Er), and the resulting solutions evaporated to dryness. The residues are dissolved in HCl and the REE precipitated as fluorides on addition of HF/NH4F solutions. The REE fluorides were collected, dissolved in a nitric/boric acid solution and the radioactivity of the resulting solutions determined by gamma spectrometry. The concentrations of REE in the NBS SRM Spinach, Orchard Leaves, Pine Needles, and Bovine Liver were found to be in the ng/g to microgram/g range. The relative standard deviations are approximately 8%. The results agreed, within experimental errors, with literature values. The distribution patterns of REE in the NBS materials relative to chondritic meteorites resemble the patterns for geological materials.