エチレンジアミン四酢酸を用いるプレカラム誘導体化／逆相分配高速液体クロマトグラフィーによる鉄鋼中の微量ビスマスの定量

Abstract

Determination of trace amounts of bismuth in steel and iron was demonstrated with high performance liquid chromatography using ethylene-diaminetetraacetate (EDTA) as a pre-column derivatizing reagent. Standard materials of steel and iron were decomposed with a mixture of nitric acid and hydrochloric acid, followed by subjected to sulfuric fuming. The residues were dissolved with 0.1 mol dm-3 hydrochloric acid to prepare digested sample solutions. Bismuth ions in the digested solution were separated from iron matrix with an anion exchange column under 0.1 mol dm-3 hydrochloric acid. The adsorbed bismuth ions on the anion exchange column could be recovered with 0.1 mol dm-3 nitric acid, quantitatively. After the recovered bismuth ions were derivatized with EDTA under pH 3.0, HPLC separation of the bismuth-EDTA complex was performed with an ODS column using an aqueous solution containing 0.01 mol dm-3 monochloroacetate buffer (pH 3.0) and 2.0×10-3 mol kg-1 of tetrabutylammonium bromide was monitored at 265 nm spectrophotometrically. A linear calibration was observed in the concentration range from 1×10-8 to 1×10-6 mol dm-3 of bismuth. The detection limit (3σ) of Bismuth was 8.8×10-8 mol dm-3, which corresponded to 0.92 ppm in iron and steel samples. An analytical recovery of a steel sample obtained with the HPLC method agreed with that obtained with GD-MS. The recoveries of bismuth added to the digested solution of iron and steel were with in 99.5 to 118%, indicating potential of the HPLC method for iron and steel analyses.