The concept of using paper chromatography on papers impregnated with liquid anion or cation exchangers is extended to the
separation of trace elements through filtration on filter papers loaded with suitable extractant. The uptake of uranium, thorium
and lanthanum from HCl and HNO3 media of different molarities by a filter paper treated with tri-octyl amine (TOA) is investigated. The effect of the different
parameters on the uptake of the studied elements is experimented. A simple and fast radiochemical procedure is developed for
the separation of La, Th and U from each other.