Determination of impurities in high-purity aluminium oxide by ICP-AES after coprecipitation with zirconium hydroxide

Abstract

Trace impurities (Fe, Si, Ca, Mg, Cu, Mn, Zn, Cr, Ni and Ti) in high-purity aluminium oxide (99.99%) were determined by ICP-AES. A coprecipitation method with zirconium hydroxide was used for the separation and concentration of the elements from matrix components. The following procedure is recommended: Fuse 1 g of aluminium oxide with a mixture of sodium carbonate (2.5 g) and boric acid (1.0 g) in a platinum crucible at 900°C for 10 min. Dissolve the melt with dilute hydrochloric acid and evaporate the solution to a syrup by heating. Dissolve the salts with water and add 30 mg of zirconium (IV). Add 2.5 M sodium hydroxide solution (40 ml) until aluminium hydroxide is redissolved. Separate the precipitate of zirconium hydroxide by filtration and wash it with water. Dissolve the precipitate with 5 ml of 6 M hydrochloric acid and make the solution finally to 25 ml with water. Run blank experiments in the platinum crucible by using definite amounts of reagents. Determine the elements in sample and blank solutions by ICP-AES. Iron and other elements were liable to transfer into a sample during fusion from the platinum crucible which had been used for various analyses. But they became to be small and reproducible or negligible by repeating to melt sodium carbonate in the platinum crucible before experiments. It was found in this work that 2–4 µg of iron and about 1 µg of copper had transferred into a sample from a platinum crucible. This method was applied for determination of 0.2–40 ppm levels of the elements in high-purity aluminium oxide samples. © 1986, The Japan Society for Analytical Chemistry. All rights reserved.