On-line solid phase extraction-capillary zone electrophoresis for the simultaneous determination of lanthanum and gadolinium at picogram per liter levels

VIZIOLI, NORA; GIL, RAÚL ANDRÉS; MARTÍNEZ, LUIS DANTE; SILVA, MARÍA FERNANDA

ELECTROPHORESIS

Wiley-VCH

Año: 2009

0173-0835

A non-specific on-line method is presented for the extraction and preconcentration of two rare earth elements (REEs) using a microcartridge containing C18 derivatized silica particles prior to their analysis by capillary zone electrophoresis. The microcartridge, named analyte concentrator, was coupled on-line to the inlet of the separation capillary (fused-silica capillary, 75 mm ID x 12 cm from the inlet to the microcartidge and 37 cm from the microcartridge to the detector). The reversed-phase sorbent quantitatively retained Gd and La as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) complexes in the presence of non-ionic micelles of polyethylene glycol tert-octylphenyl ether (Triton X-100), enabling sample clean-up and concentration enhancement with minimum sample handling. The REEs chelates were released from the sorbent with methanol and then analyzed by CZE with diode array detection. A background electrolyte of 20 mM sodium tetraborate containing 8% ACN, pH 9.0, was found to be optimal for the separation of metal chelates. The concentration limits of detection (CLODs) were lowered to picogram per liter levels (20 pg/L for La and 80 pg/L for Gd). A 1000-fold improvement in concentration sensitivity for La- and Gd-5BrPADAP complexes with respect to CZE without preconcentration was reached.