In this quest you will have to separate Po-210 and Pb-210 from interfering radionuclides using Sr Resin column.
First you will dissolve precipitate in HCl and H₂O₂. After successful evaporation until dryness, you will have to dissolve residue in 2 M HCl. Now the sample is ready for separation on Sr Resin column.
Before you can pour sample on Sr Resin column you will have to condition it with 2 M HCl and then separate Po with 6 M HNO₃ and Pb with 6 M HCl.
How this is performed in real lab you can watch here.