Determination of trace amounts of carbon in high-purity iron by infrared absorption after combustion: pretreatment of reaction accelerator and ceramic crucible

Pre-treatment procedures for analysis for determination of trace carbon amounts in high-purity iron was investigated. Carbon in metal samples has been determined with an infrared absorption method after combustion. An analytical sample with a mixed tungsten-tin as a reaction accelerator in a ceramic crucible is subjected to combustion in oxygen atmosphere. Contamination carbon species in the oxygen gas, the ceramic crucible and the accelerator cause analytical blank value. The oxygen gas was purified. The ceramic crucible was heated at 1623 K for more than 20 min in ambient atmosphere. Moreover, the accelerator was heated in ambient atmosphere at 1003 K for 15 min with stirring it every 5 min during heating. Consequently, the carbon blank could be completely removed, and trace amounts of μg·g^-1 level carbon in high-purity iron could be determined in the proposed method.