Determination of Trace Amount of Carbon in Highly Purified Iron by Using Gasification Method in Hydrogen Gas Atmosphere

A new method for the determination of trace amounts of carbon in highly purified iron has been developed. The method is based on the gasification of carbon by the heat of a sample in hydrogen, and the detection of extracted gases, such as methane and carbon monoxide, by the use of flame ionization detector-gas chromatography. Highly purified iron was prepared in the size of φ0.1 mm × 10 mm, and set in a quartz tube. The sample is pre-heated at 673 K in a nitrogen and oxygen (20.1 vol.%) gas mixture so as to eliminate adsorbed carbon on the surface of the sample (surface carbon). Subsequently, the sample is heated at 1373 K for 10 min in hydrogen gas. Carbon in the sample (bulk carbon) diffuses thermally, and is extracted as methane and carbon monoxide. Bulk and surface carbon of the sample can be determined separately by the proposed method. Carbon content about 4 μg/g in highly purified iron can be determined with a relative standard deviation (RSD) of about 10%. The determination limit (10 σ of blank values) of this method is 1 μg/g carbon in a 1 g sample. The time required to analyze one sample is about 50 min. The determined values of carbon by proposed method agree well with the reference values obtained by an infrared absorptiometric method after combustion.