On‐line solid phase extraction CZE for the simultaneous determination of lanthanum and gadolinium at picogram per liter levels |
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Authors: | Nora Vizioli Raúl Gil Luis Dante Martínez María Fernanda Silva |
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Institution: | 1. Department of Analytical Chemistry and Physicochemistry, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina;2. National Council of Scientific and Technological Research, Buenos Aires, Argentina;3. INQUISAL, Department of Chemistry, National University of San Luis, San Luis, Argentina;4. Faculty of Agronomic Sciences, National University of Cuyo, Mendoza, Argentina |
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Abstract: | A non‐specific on‐line method is presented for the extraction and preconcentration of two rare earth elements using a microcartridge containing C18‐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 μm id ×12 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. |
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Keywords: | CZE Environmental analysis Gadolinium Lanthanum On‐line SPE |
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