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 alpha-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 nn. Electrokinetic injections and transient isotachophoresis were implemented to stack the analyte ions into more concentrated zones. On-line preconcentration factors were determined to be similar to 700 and resulted in limits of detection for La3+, Ce3+, Pr3+, Nd3+, Sm3+, and Eu3+ in the low-ppb range (6-11 nM).