[en] The extraction of Np(IV) with TCMA-xylene from mixed mineral acid solutions as well as from mixed aqueous organic media is investigated. It was found that the extraction was increased by the addition of H₂SO₄ to HCl medium while decreased by the addition of H₂SO₄ to HBr or KI solutions. In mixtures of HNO₃ with various organic solvents, the influence is found to depend on the dielectric constant and the chain length of the organic solvent introduced into the extraction system. The extraction of 14 elements is also tested at the optimum condition for Np(IV) extraction. On the bases of the obtained results, separation conditions are mentioned and analytical advantages are recommended. (author)