1 research outputs found
Multistep pH-Peak-Focusing Countercurrent Chromatography with a Polyethylene Glycol-Na<sub>2</sub>SO<sub>4</sub> Aqueous Two Phase System for Separation and Enrichment of Rare Earth Elements
Multistep pH-peak-focusing countercurrent chromatography
was developed
for separation and enrichment of rare earth metal ions using a polyethylene
glycol-Na<sub>2</sub>SO<sub>4</sub> aqueous two phase system (ATPS)
and pH stepwise gradient elution. Metal ions in a sample solution
are chromatographically extracted in a basic stationary phase (polymer-rich
phase of the ATPS) containing a complexation ligand such as acetylacetone
at the top of the countercurrent chromatography (CCC) column. After
the sample solution is introduced, the mobile phases of which the
pH values have been adjusted with buffer reagents are delivered into
the column by stepwise gradient elution in order of decreasing pH.
Each metal ion is concentrated at a pH border formed between the zones
of different pH in the CCC column through extraction with a complexing
agent into the stationary phase at the front side of the border (basic
region) and back extraction into the mobile phase at the back side
of the border (acidic region), moving toward the outlet of the column
with the pH border. Mutual separations of LaÂ(III), CeÂ(III), NdÂ(III),
YbÂ(III), and ScÂ(III) were achieved by the present method using five
step pH gradient elution, and each rare earth metal ion was effectively
enriched at each of the five pH borders. The mechanism for formation
of pH profile of the column effluent and the potential of this technique
for preparative scale separation are also discussed