DYNAMIC ION-EXCHANGE CHROMATOGRAPHY FOR THE DETERMINATION OF LANTHANIDES IN ROCK STANDARDS

A high-performance liquid chromatographic procedure has been developed and tested for the determination of rare earth element (REE) concentrations in United States Geological Survey rock standards AGV-1, GSP-1 and G-2. The procedure involved acid digestion of sample in PTFE pressure bombs, group separation of REEs, followed by elution of individual lanthanides using alpha-hydroxyisobutyric acid in the presence of hydrophobic ions on a C-18 bonded silica reversed-phase column. The eluted REEs were monitored by visible spectrophotometry at 520 nm after post-column reaction with pyridylazoresorcinol. This reversed-phase partition system is suited to separate and detect all lanthanides elements in less than 20 min with good reproducibility. Comparison of the results with literature values shows an agreement of +/-5% for all elements. An internal standard deviation of +/-0.5% was found for a single analysis, while triplicate analysis showed a standard deviation of 1-2%.