[en] Is intended for definition of small impurity concentration of transuranium elements in biological tests, on first for definition of the contents of plutonium in biological tissue. Threshold of detection 10¹⁰ atoms is received, for plutonium 239 it corresponds to a registered level of activity 0,01 Bq. The limiting sensitivity, which can be achieved on the basis of the created experimental unit, makes 10⁸ atoms or 10^-4 Bq for plutonium 239, and will allow, for example, to fix presence of a required element in test with weight 0.001 mg and concentration 10^-6. The extremely high selectivity of detection will ensure revealing of element at the presence of any masking substances of an organic and inorganic nature