Speciation problems solved with NAA: Some actual cases for Hg, V, Cr, As and Se

Abstract

The evaluation of the eco-toxic consequences of heavy metals on the biosphere requires assessment of their biological effects. This involves the determination of the different ionic species and the various chemical forms of each element. For many elements, the usual electrochemical methods for the analysis of different chemical species do not meet the required sensitivity; ppm or even ppb concentration ranges represent often the actual content of many matrices. For many elements as Hg, V, Cr, As, and Se one of the most sensitive method of trace determinations down to the ppb level is the NAA. Unfortunately this method gives information only on the total number of nuclei present, regardless to their outer structure and chemical forms. In this work, some examples are given of the feasibility of NAA to the determination of trace amounts of different chemical species of some heavy metals, when coupled to specific separation procedures.