Application of a modified atomic absorption spectrometer for the determination of iron traces in gaseous hydrogen chloride

Abstract

The analysis of reactive gases, especially the determination of heavy metals, is of increasing importance because of their use in the production of semiconductors. Owing to the increasing requirement for high purity gases, efficient methods of analysis have to be developed for the determination of metallic contaminants. Up to now some analytical procedures have been described, but no reliable method for the on-line monitoring of reactive gases has been established. In this publication, an analytical procedure is described for the determination of iron in gaseous hydrogen chloride by means of a modified atomic absorption spectrometer. A gas inlet was realized by a special graphite capillary. The sampling was carried out by a modified ‘bypass-backflush-balancing’ gas injection system as described previously by Schram. Typical parameters, e.g., ashing and atomization temperature, the temperature programme and the gas injection volume were optimized. The calibration was carried out using iron standard solutions. The detection limit for the described procedure was 0.7 ng ml–1 iron (temperature = 25 °C). The reproducibility of the absorbance signals for iron in hydrogen chloride was 4%(n= 6).