The work was focused on the experimental determination of the separation-extraction properties of solid extrahent DIPHONIX (Eichrom Industries, USA) depending on the used eluent. Extraction properties were tested for plutonium, americium, curium, and uranium. The used mobile phases were hydrochloric acid and nitric acid at various concentrations. The aim was to find the most appropriate combination of mobile phase and eluent, which would lead to the highest possible yield. The most commonly used eluent published in literature is 1-hydroxyethane 1, 1-diphosphonic acid (HEDP, Etidronic Acid). Based on the research the specific compounds were selected which are generaly known for their complexing properties, such as the salts of oxalic acid and citric acid at different concentrations. Activities of the samples obtained by elution were measured by liquid scintillation spectrometry.