Radiation monitoring of strontium-90 is important for solving nature conservation and ecological problems. The analysis of literature sources shows us that the methods for determining strontium-90 are long, rather complicated and multi-stage, determination errors and underestimated results are not excluded. It is necessary to select the optimal conditions for the determination of this isotope, simplify the analysis and accelerate, while reducing the detection limit to 0.1 Bq/L. As a result of the work, 5 sorbents for preliminary concentration of strontium were studied. Based on a comparison of the sorption characteristics, the best sorbents were selected, and the effect of pH on the degree of strontium sorption was investigated. For the selective isolation of strontium-90 on a thin-layer MnO2-CTA sorbent, the effect of pH and the possibility of separating cesium-137 were studied.