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Methods for the field determination of rhenium in plants have been developed. The speciation of rhenium in solutions throughout the process of sample preparation has been investigated. It has been shown that, in the initial ethanol and water-salt extracts, rhenium occurs as perrhenate ions. Perrhenate ions have been established to be partially reduced in time to give Re(VI). Since test methods have been developed for determining rhenium as perrhenate-ions, their partial reduction in the process of sample preparation can lead to an low level of the results. The optimal conditions for preserving rhenium as perrhenate ions have been determined. Two procedures (in four versions) providing the determination of as low as 5 ng of rhenium in a 1-g sample with an error below 23% have been proposed. The developed procedures have been applied in the places of the collection of plant materials for the regional investigation of the occurrence of rhenium in the territories of different ore contents. DOI: 10.1134/S1061934810050163, We have previously found that a rare trace element rhenium, of which the average abundance in the earth's crust is 7 x [10.sup.-8]% (Vinogradov's clark [1]), is efficiently accumulated in [...]

Abstract -- Methods for rhenium extraction from plant materials were studied using model systems and the [.sup.186.Re] isotope. Conditions are described for the quantitative extraction of rhenium with acid and [...]