Analytical separations of lanthanides and actinides by capillary electrophoresis

Abstract

The separation of lanthanide and actinide elements belongs to one of the most challenging tasks of the separation science, due to a great similarity in their physical and chemical properties. The electrophoretic separation can be accomplished in the presence of suitable complex-forming agents, from which alpha-hydroxyisobutyric acid (HIBA) has been used most often. In the most effective capillary electrophoretic mode--capillary zone electrophoresis (CZE)--a complete separation of lanthanide ions can be accomplished within a few minutes. Various electrophoretic methods can be relatively easily adopted for the determinations of individual lanthanide elements in certain kinds of technical materials, concentrates, precursors, etc., where the high speed and low costs of analysis characteristics of capillary electrophoresis (CE) may be advantageously exploited. Electrophoretic techniques may also be employed for speciation studies, especially for examinations of the behavior of actinides in the environment.

Highly sensitive determination of lanthanides by capillary electrophoresis with direct visible detection after precapillary complexation with aromatic polyaminocarboxylate and additionally applying dynamic ternary complexation with nitrilotriacetic acid

“…The electropherogram at pH 12 was rather similar to that of Ln-ABEDTA complexes (data not shown) [16]. The order of migration was found to be from light to heavy rare earth ions, which was reasonable in terms of the ionic radii of Ln 31 , and this tendency has been observed in other reports about Ln 31 separation [27,[38][39][40][41]. Regarding the ligand design for CE, a large ligand frame, such as NBD-ABEDTA, is generally undesirable because the increase of the ligand size hardly makes any difference in the size of the complexes if the center-metal ions are different, which plays a central role in controlling the mobility of the complexes.…”

“…5 and 6). This inversion is unusual in the separation science of Ln ions [38]. To our knowledge, the invert- Figure 6.…”

“…It is expected that the larger charge density on hard metal ions, such as Ln ions, provides a stronger bond to ligands with charge-charge interaction, leading to a larger stability constant. Separation has been carried out based on the difference of the complexing stability among Ln ions in most separation systems [27,38]. In these studies, heavier (harder) Ln 31 , which more strongly forms an anionic complex, migrates more swiftly toward the positive end when anionic ligands are employed.…”

“…31 . This LOD is remarkable without pre-or on-column concentration (typically mM-level) [38], though the detection of low nanomolar…”

An evaluation of the experimental approaches to detection of small ions in CE

“…[22], those for lanthanoids and actinoids in ref. [23]. Detection methods applied to microchip and conventional CE analysis of explosives are discussed in ref.…”