The study of the interphase distribution of a large number of target and impurity components of highly radioactive wastes is a necessary and very laborious stage in the creation of new extraction systems. With the quantitative extraction of cesium-137 and strontium-90 from spent nuclear fuel for the purposes of further industrial and commercial use, difficulties arise associated with competing complexation and the concomitant extraction of impurities of stable elements. We have developed an express method for determining the distribution ratios of metals using inductively coupled plasma mass spectrometry (ICP-MS). A feature of the proposed method is the joint extraction of trace amounts of all studied metals, followed by direct ICP-MS analysis of equilibrium aqueous and organic phases.