Highly-sensitive simultaneous detection of lanthanide(III) ions as kinetically stable aromatic polyaminocarboxylato complexes via capillary electrophoresis using resolution enhancement with carbonate ion

摘要

An aromatic polyaminocarboxylate ligand, 1-(4-aminobenzyl)ethylenediamine-N,N,N,N-tetraacetate (ABEDTA), is proposed as a complexing reagent in the pre-capillary mode so as to form kinetically inert Ln(III) complexes, meaning that no added ligand is necessary in alkaline carrier buffer solutions. In addition, highly-sensitive detection is possible through a light-absorbing moiety of an aminobenzyl group in the ligand. The fine-tuning of the electrophoretic mobilities of the Ln-abedta complexes is successfully achieved by adding an auxiliary carbonate ion ligand which alters the charge-to-size ratio of the complexes through fast exchange equilibria in a carrier buffer. In fact, all of the complexes are detectable with very similar analytical sensitivity and acceptable resolution (except for Ln = Sm, Eu, Gd) by using NaOH-borate carrier buffer solution at pH 12.35 with 20 mM of Na_2CO_3. A typical detection limit for Tb(III) ion (to 3σ) is as low as 0.94 μM, which translates to an absolute amount of 9.4 fmol in a 1.0 * 10~(-8) dm~(-3) (10 nL) injection.