Matrix removal by thermal fluorination in the graphite furnace atomic absorption analysis of high purity aluminum

A halogen assisted thermal purification method was developed with the use of Ar+1% (v/v) CHF3 internal furnace gas and applied specifically to the determination of iron impurities in high-purity aluminum. The samples were applied in the form of hydrochloric acid solution, and the alumina formed by hydrolysis from the chloride salt was reacted with the halocarbon in the pyrolysis step to attain a complete volatilization of the matrix without loss of the analyte (Fe). As a result, no interfering background in the 200–340-nm spectral range was observed that was otherwise very intensive without halogenation. The deuterium lamp background correction method was appropriate up to a sample amount of 400 μg aluminum, resulting in a characteristic concentration of 3.7 ng g−1 (ppb) Fe in the solid aluminum sample.