Lanthanides—Separation and Analysis

Having separated rare earth elements, non-selective chromogenic reagents are often used for their detection and/or quantitative analysis. A spectrophotometric study involving rare earth elements and Arsenazo III as a chromogenic reagent has been conducted to establish the dominant equilibria and complexes involved. The results illustrate that the variation in the concentration of complexing agents, for instance a-hydroxyisobutyric acid, which are used to elute the rare earths from columns, is the dominant cause for differences in the intensity of the peaks in chromatograms. The results are used to explain how reliable results can be obtained and inconsistencies regarding interlaboratory comparisons can be avoided.