2008 Volume 94 Issue 3 Pages 80-85
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.