[en] To improve the sensitivity of the method of Pu determination in specimens we applied two additional steps of chemical separation of Pu from U. After the usual chemical separation of Pu we used second step with ion-exchange column, where the ions of U⁴⁺ were absorbed by sorbent and Pu³⁺ ions remains in solution. For converting Plutonium to Pu³⁺ state the electrochemical procedure has been used. After the electrochemical separation procedure the solution was deposited onto quartz glass. Then the quartz glass plates were inserted into the gas mixture flow (SOCL₂+air) at the temperature 650 deg. C. Such a procedure extracts ≥90% U from Pu layer. Now we provide the chemical separation of Pu from U by a factor ≥10⁷. It means that now we are able to perform the routine Pu analysis at the level of sensitivity 10^-14-10^-15 g/g. By using combined n-γ activation technique we can determine the Pu content in the small fragments of tissues of living species with the weight as small as 0,05-0,1 gram. The new technique could be used in routine analysis of Pu in population of heavily Pu damaged regions (Chernobyl, Ural Region, Semipalatinsk)