Chemical reactions of tellurium in graphite tubes of atomic absorption spectrometry

The chemical reactions of tellurium were investigated in uncoated, pyrolytic graphite-coated, and zirconium-treated polycrystalline electrographite tubes. After drying, tellurium is present as TeO2, which is reduced by the graphite to the volatile suboxide TeO. This molecule was detected in the gas phase by molecular absorption spectroscopy. In coated tubes, this reduction process occurs at lower temperatures compared to uncoated and Zr-treated tubes, and shows a faster reaction rate. The suboxide is reduced to elemental Te on collision with the graphite tube wall. This transport process via the gas phase was observed by vaporization from L’vov platforms and subsequent separate atomization from wall and platform. In uncoated tubes, tellurium could be stabilized to temperatures above 1200°C due to intercalation, which was proven by re-oxidation experiments.