Mechanisms of magnesium chloride interferences on zinc in electrothermal atomic absorption spectrometry using a dual cavity platform

The mechanism of interference due to magnesium chloride on the determination of zinc in electrothermal atomic absorption spectrometry has been investigated using a dual cavity platform which has two separate cavities instead of one. It allows the analyte and interferent to be introduced at separate locations on the platform without mixing in the condensed phase; therefore, in principle, gas-phase and condensed phase interferences can be distinguished. In the presence of magnesium chloride, zinc chloride is formed both in the condensed phase and upon reaction between analyte species and HCl(g) formed from the hydrolysis of magnesium chloride, and is lost in molecular form during the pyrolysis or early in the atomization steps. At low pyrolysis temperatures, where magnesium chloride is not significantly hydrolysed but rapidly decomposes during the atomization step, expulsion of analyte from the furnace together with matrix gases and/or gas-phase reaction between zinc atoms and chlorine in this step are responsible for signal depression.