On-line solid phase extraction CZE for the simultaneous determination of lanthanum and gadolinium at picogram per liter levels.
A non-specific on-line method is presented for the extraction and preconcentration of two rare earth elements using a microcartridge containing C(18)-derivatized silica particles prior to their analysis by CZE. The microcartridge, named analyte concentrator, was coupled on-line to the inlet of the separation capillary (fused-silica (FS) capillary, 75 microm id x12 cm from the inlet to the microcartidge and 37 cm from the microcartridge to the detector). The reversed-phase sorbent quantitatively retained gadolinium (Gd) and lanthanum (La) as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complexes in the presence of non-ionic micelles of polyethylene glycol tert-octylphenyl ether, enabling sample clean-up and concentration enhancement with minimum sample handling. The rare earth elements 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 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-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complexes with respect to CZE without preconcentration was reached.
Vizioli
Nora
N
Department of Analytical Chemistry and Physicochemistry, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina.
Gil
Raúl
R
Martínez
Luis Dante
LD
Silva
María Fernanda
MF
D001391:Azo Compounds / Q000737:chemistry; D019075:Electrophoresis, Capillary / Q000379:methods*; D005682:Gadolinium / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007811:Lanthanum / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D052616:Solid Phase Extraction / Q000379:methods*; D014881:Water Supply
D001391:Azo Compounds; C037882:2-(5-bromo-2-pyridylazo)-5-diethylaminophenol; D007811:Lanthanum; D005682:Gadolinium