Enrichment and determination of zinc by high-speed countercurrent chromatography

The capability of high-speed countercurrent chromatography (HSCCC) has been investigated for enrichment and determination of metal ions at trace levels. Separation of selected divalent metal ions was performed using a small coiled column. A hexane solution of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPA) was employed as the stationary phase. Loaded divalent metal ions such as Ni, Co, Cu, and Zn were chromatographically eluted in the order of increasing extractability by passing a mobile phase buffered at a desired pH. Individual metal ions showed good linearity between concentrations and chromatographic peak areas of the absorbance, as detected by postcolumn reaction with 4-(2-pyridylazo)resorcinol (PAR). Metal ions enriched into the stationary phase from a sample solution were separated into individual metal ions. The trace quantity of zinc in natural mineral water was determined by enrichment separation through an HSCCC column.