Abstract: A kinetic approach and other informations were employed to study the mechanism of Cd ashing and atomization when NH₄H₂PO₄ was used as a modifier. During the pyrolysis stage Cd_x(PO₃)_n produced and a large amount of NH₄H₂PO₄ dehydrated to form metaphosphate with chain or ring shape. This may result in the physical embedment of Cd. So both chemical and physical factors lead to the rise of the pyrolysis temperature. During the atomization stage, the analyte atomization was considered to be governed by the decomposition of this meta phosphate.

Key words: graphite furnace atomic absorption spectrometry, kinetic model, Arrhenius plot