The preconcentration of strontium using a solid phase separation technique with selective micelle forming complexant has been studied. Di-2-ethylhexylphosphoric acid and its thio- and dithio derivatives were used as modifiers. The goal of this work was to study the influence of physico-chemical parameters on recovery of strontium after its preconcentration on reverse phase (Si–C-18) using micelle modifiers.