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 developed. Among other usual means of attack (nitric acid and hydrogen peroxide) it also includes an hydrofluoric acid treatment followed by an evaporation to dryness in order to dissolve elements which may be retained by the insoluble silica residue. Already observed using dry ashing procedures, this particular problem associated with the plant matrix analysis is widely discussed. The proposed total wet digestion method 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 reference plant materials for main, minor and trace elements. Unfortunately, the determination of mercury requires an alternative mineralization procedure because significant losses of Hg are observed during the evaporation to dryness. In this case a simple mineralization with sulphuric acid and hydrogen peroxide using classical or microwave heating devices allows volatilization losses of mercury to be overcome.