Separation of inorganic ions by high-speed countercurrent chromatography with an aqueous biphasic system

Abstract

The optimum experimental conditions for J coil planet centrifuge high-speed countercurrent chromatography (HSCCC) with aqueous biphasic systems consisting of polyethylene glycol (PEG) and sodium sulfate were investigated using some inorganic anions as model compounds. The PEG-rich upper phase was used as the stationary phase and the salt-rich lower phase was used as the mobile phase. In order to eliminate fluctuations of the base line of chromatograms owing to emulsification caused by excessive mixing of the two phases, water was mixed with the eluate from the column prior to UV detection. The resolution of iodate ion and iodide ion increased with an increase in the revolution speed of the Teflon tube column holder although the volume of the stationary phase retained in the column decreased. This was due to an improvement of the separation efficiency, shown as an increase in theoretical number of sample compounds. The increase in the flow rate of the mobile phase caused a decrease in the stationary phase volume. However, the resolution did not depend on the flow rate in the range studied. This may be interpreted in terms of relatively high distribution ratios of the inorganic anions used in this study. Separation of some inorganic anions and that of chromium (III) ion and chromate(VI) ion were easily accomplished by HSCCC with PEG#1000-16.7% (w/w) Na2SO 4 aqueous biphasic system.