Metal ions are known to be absorbed and concentrated by plant biomass. In distinction from ionexchange resins, which usually contain monofunctional groups, polyfunctional compounds of biomass exhibit unique capacity of accumulating metal ions, sometimes unrelated to classical sorption. This property can be used for different technological, analytical, and biological purposes, including the extraction of metals from industrial wastewater, cleaning contaminated areas, exploration of ore deposits (as biochemical indicators), etc.The scanty available data indicate that the concentration of rhenium in plants exceeds its concentration in the earth's crust by three to four orders of magnitude [1,2], which corresponds to anomalous accumulation, according to the currently accepted classification [3].Search for new sources of rhenium, including unconventional ones, is a burning problem because of the low rhenium concentration in the earth's crust (its clarke is 1 × 10 -7 %) and the great importance of this element for industry (aerospace, nuclear, electronic, oil-processing, and other). Of current interest is also the development of procedures for determining rhenium in plant materials in a wide concentration range and the thorough monitoring of the plant cover of different geographic regions, which is an essential condition for the detection and registration of anomalous biogeochemical fields of rhenium mineralization and the revelation of correlations between the concentrations of rhenium in water, soils, and plants. The information gained can be used in biotechnology and ecology to study rhenium effect on living organisms and the identification of rhenium species responsible for its migration, immobilization, and distribution in the nature.The aim of this work was to develop procedures for the determination of rhenium in plant biomass that are suitable for stationary and field conditions. It is known that the limiting step of routine analyses is sample preparation, which should not only ensure the complete conversion of the analyte to appropriate species but also meet the requirements of the method selected. Therefore, special attention was given to different methods for the decomposition of plant materials and to the distribution of rhenium among the steps of sample preparation. The radioactive 186 Re tracer was used.Rhenium was determined using catalytic methods based on the redox reactions of Sulfonitrazo R ( c min = 0.2 ng/mL) [4] and dimethyldithiooxamide ( c min = 1 ng/mL) [5] that we had developed previously, as well as solid-phase spectrophotometry ( c min = 0.1 µ g Re) [6] and neutron activation analysis. EXPERIMENTAL Apparatus. Experiments were conducted using a programmable PDP-18M furnace with two chambers (evaporation and ashing), a Specord M-40 spectrophotometer, and a single-channel NC-428B nuclear analyzer (Hungry) with a γ detector (model no. 35 114 059).Reagents. The stock solution of rhenium (1000 µ g/mL) was prepared by dissolving 0.1553 g KReO 4 in 100 mL of water; working solutions containing 1 µ g...
