イオン交換吸着‐イオン対溶離法による鉄鋼分解液中からの微量ビスマスの分離濃縮と黒鉛炉原子吸光法による定量

Abstract

A unique preconcentration method “ion-exchange preconcentration followed by ion-pair elution” was applied to separation and preconcentration of trace amounts of bismuth in a digested solution of iron and steel. Bismuth(III) was derived to anionic iodo complex prior to preconcentration. The bismuth complexes were adsorbed on cotton impregnated with capriquat through ion-exchange reaction, followed by being recovered as ion-pair of capriquat by elution with methanol. Since iron ions in the digested solution were reduced into divalent state with ascorbic acid, which also works as an anti-oxidized agent of iodide ions, matrix irons did not form iodide complexes, leading to no adsorption on the cotton. More than 99.99% iron could be removed by rinse with a solution containing 0.8 mol dm−3 ascorbic acid and 0.5 mol dm−3 hydrochloric acid. The described preconcentration could be successfully combined with graphite furnace atomic absorption spectrometry (GF-AAS) due to the removal of capriquat with ashing stage in the GF-AAS protocol. Combination of 10-fold preconcentration and GFAAS measurement allowed us to determine trace amounts of bismuth in a digested solution of iron with a detection limit (3σ) of 4.4×10−9 mol dm−3, which corresponds to 4.6 ppb in iron and steel. The combined method was successfully applied to determination of bismuth in certified reference materials of iron and steel.