Transient Isotachophoretic−Electrophoretic Separations of Lanthanides with Indirect Laser-Induced Fluorescence Detection

Indirect laser-induced fluorescence was used for the detection of several lanthanide species separated by capillary electrophoresis. Quinine sulfate was the fluorescent component of the background electrolyte, and α-hydroxyisobutyric acid was added as a complexing agent to enable the separation of analyte ions that have similar mobilities. The UV lines (333−364 nm) of an argon ion laser were used as the excitation source with a diode array detector for monitoring the fluorescent emission at 442 nm. Electrokinetic injections and transient isotachophoresis were implemented to stack the analyte ions into more concentrated zones. On-line preconcentration factors were determined to be 700 and resulted in limits of detection for La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, and Eu³⁺ in the low-ppb range (6−11 nM).