The organic-inorganic composite support, in which silica particles are coated with styrene-divinylbenzene copolymer, is impregnated by a CMPO extractant (or CMPO-impregnated adsorbent) and used to fill the separation column. The nuclides and their spatial distribution can be identified without destroying the sample from the neutron energy and the decrease in number of neutrons transmitted through the column, respectively.