Tungsten atomizer-action of modifiers

摘要

Tungsten atomizers have been used for electrothermal atomization in atomic absorption spectrometers since 30 years. Various matrices have been analyzed with and without modifiers. Various modifiers have been used, e.g. NH_4H_2PO_4, Pd, Pd and Mg, Al(NO_3)_3, which are common in graphite furnace too. Action of modifiers with a tungsten surface is different from action on grapite, because the reaction of tungsten with analyte, protective gas (hydrogen) and modifiers causes reduction of analytes. We have studied the interaction of Cd with the tungsten surface, hydrogen and NH_4H_2PO_4 or Pd as nitrate after each step of the heating program. Morphology of newly produced compounds on the tungsten surface was studied by an elecgron raster microscope and energy dispersive X-ray analysis. The following results and their comparison with theoreticfal assumptions enables us to suppose, that action of NH_4H_2PO_4 or Pd as nitrate do not realize such shift of temperature as observed when using a graphite furnace.