[en] Extraction of microamounts of REE of the cerium subgroup with nitrates of tertiary amines of different structure has been studied. It has been found that the nature of the element being extracted affects the stoichiometry of REE extraction with amines. Due to this, a change in the amine concentration leads to a different variation of the distribution coefficients of REE. As a result, not only the separation coefficients of these elements are altered, but the order of their extractibility can be distorted. The general tendency is deterioration of selectivity of REE extraction with increasing amine concentration