Extraction preconcentration of uranium and thorium races in the analysis of bottom sediments by inductively coupled plasma mass spectrometry

A procedure was developed for determining trace amounts of uranium and thorium isotopes in bottom sediments from Lake Baikal. This procedure involves sample decomposition, the coextraction of uranium and thorium with trioctylphosphine oxide, the quantitative back extraction after diluting the extract with caprylic acid, and the ICP MS analysis of the back extract. The procedure was verified by analyzing a BIL-1 Lake Baikal bottom silt standard reference material using the developed procedure and independent methods. The detection limits of abundant uranium and thorium isotopes are restricted by blank measures and equal to I X 10(-7) mass %. The detection limits for 214 U and Th-230 are 4 x 10(-10) and 6 x 10(-10) mass %, respectively.