CRITICAL DISCUSSION ON THE NEED FOR AN EFFICIENT MINERALIZATION PROCEDURE FOR THE ANALYSIS OF PLANT-MATERIAL BY ATOMIC SPECTROMETRIC METHODS

A wet digestion method for the mineralization of plant samples was dev eloped. Among other usual means of attack (nitric acid and hydrogen pe roxide) it also includes an hydrofluoric acid treatment followed by an evaporation to dryness in order to dissolve elements which may be ret ained by the insoluble silica residue, Already observed using dry ashi ng procedures, this particular problem associated with the plant matri x analysis is widely discussed, The proposed total wet digestion metho d may be applied to plant samples using both classical heating devices (sand-bath) or microwave open systems and its validity was confirmed by analyses by inductively-coupled plasma atomic emission spectrometry and electrothermal atomic absorption spectrometry of several referenc e plant materials for main, minor and trace elements, Unfortunately, t he determination of mercury requires an alternative mineralization pro cedure because significant losses of Hg are observed during the evapor ation to dryness. In this case a simple mineralization with sulphuric acid and hydrogen peroxide using classical or microwave heating device s allows volatilization losses of mercury to be overcome. (C) 1998 Els evier Science B.V.