SELENIUM SPECIATION IN ENVIRONMENTAL MATRICES: A PRELIMINARY STUDY ON PLANTS

The determination of selenium in plants is here taken into consideration in order to carry out a speciation study. Two methods have been defined; the first one based on differential pulse cathodic stripping voltammetry (DPCSV) for very low selenium concentration levels and the second one based on inductively coupled plasma atomic emission spectrometry (ICPAES) suitable for higher levels. Different steps making up the methods have been optimized. The method for trace levels has been validated through the analysis of NIST SRMs. The methods have been used to determine the selenium in fruits (capsule and seed) of a selenium-enriching plant from Venezuela (Lecytis Ollaria). The selenium content in capsules and in seeds was evaluated; the seed contains ? 5000 mg kg-1 as total selenium, of which almost 50% is soluble in solvents. In this fraction inorganic hexavalent selenium is the prevailing form while only ? 5 mg kg-1of Se(IV) are present.