The work was fo cused on the ex per i men tal de ter mi na tion of the sep a ra tion-ex trac tion proper ties of solid extrahent DIPHONIX (Eichrom In dus tries, USA) de pend ing on the used eluent. Ex trac tion prop er ties were tested for plu to nium, am er i cium, cu rium, and ura nium. The used mo bile phases were hy dro chlo ric acid and ni tric acid at var i ous con cen tra tions. The aim was to find the most ap pro pri ate com bi na tion of mo bile phase and eluent, which would lead to the high est pos si ble yield. The most com monly used eluent pub lished in lit er a ture is 1-hydroxyethane 1, 1-diphosphonic acid (HEDP, Etidronic Acid). Based on the re search the spe cific com pounds were se lected which are generaly known for their complexing prop er ties, such as the salts of ox alic acid and cit ric acid at dif fer ent con cen tra tions. Ac tiv i ties of the samples ob tained by elu tion were mea sured by liq uid scin til la tion spec trom e try.