CONCENTRATIONS OF RARE-EARTH ELEMENTS IN HUMAN BRAIN-TISSUE AND KIDNEY-STONES DETERMINED BY NEUTRON-ACTIVATION ANALYSIS

Determinations of rare earth element (REE) contents in biological (especially human) samples are sparse. The REEs are mainly incorporated into the human body via ingestion of (predominantly) food and by inhalation of dust particles, and are mostly excreted. A small amount may enter the blood stream through ion exchange, and can be deposited in the organs. Because of the low contents of the REEs in plasma and urine we measured REE concentrations in freeze-dried human brain tissue and in kidney stones. The measurements were carried out by neutron activation analysis, and yielded concentrations for up to nine REEs in each sample. We found that there is some difference between the REE patterns for apatite and oxalate kidney stones, and that the REEs are fractionated compared with typical REE contents in plants.