STUDIES ON THE BIOLOGICAL EFFECTS OF RARE-EARTH ELEMENTS .1. METHOD FOR ANALYSIS OF DYSPROSIUM (DY), EUROPIUM (EU), YTTERBIUM (YB) AND YTTRIUM (Y) FROM THE BIOLOGICAL-MATERIALS

The analytical method of 4 kinds of rare earth elements i.e. dysprosium (Dy), europium (Eu), ytterbium (Yb) and yttrium (Y) from the biological materials were investigated. 1) Three kinds of methods, i.e. atomic absorption spectrometry (AAS), flame emission spectrometry (FES) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were compared. Most sensitive and reliable method was ICP-AES, so the determination of 4 kinds of rare earth elements was performed by ICP-AES. 2) Two kinds of solvent extraction method were investigated. None of APDC-MIBK (ammonium pyrrolidinedithiocarbamate/methyl isobuthyl ketone) system nor D2-EHPA (di(2-ethylhexyl)phosphoric acid) system revealed sufficient results. 3) Dry ashing procedure was investigated for the biological materials. Recoveries of Dy, Eu, Yb and Y (25-2500 ppm added) were 44.0-96.5% for the liver, whole blood, spleen and kidney for which the ashing was complete; contrarily, those were 35.5-78.9% for the feces and femur for which the ashing was incomplete. 4) Wet digestion method was investigated for the biological materials. Recoveries of Dy, Eu, Yb and Y were 77.6-100.7% in case of H2SO4-HNO3 digestion (250 ppm added) and 85.3-100.5% in case of HNO3 digestion (25 ppm added). The HNO3 digestion method was better than the H2SO4-HNO3 digestion method because of no CaSO4 precipitation in the former method. Therefore, it was suggested that the best analytical method for these 4 kinds of rare earth elements from the biological materials was the combination of wet digestion method by using HNO3 with ICP-AES.