Determination of iodide in samples with complex matrices by hyphenation of capillary isotachophoresis and zone electrophoresis
2007
Pantůčková, Pavla | Urbánek, Marek | Křivánková, L (Ludmila)
A method has been developed for the determination of iodide in mineral water, seawater, cooking salt, serum, and urine based on hyphenation of capillary ITP and zone electrophoresis. A commercially available instrumentation for capillary ITP with column-switching system was used. ITP served for removal of chloride present in the analyzed samples in a ratio of 10⁶-10⁷:1 to iodide, zone electrophoresis was used for evaluation. Isotachophoretic separation proceeded in a capillary made of fluorinated ethylene-propylene copolymer of 0.8 mm id and 90 mm total length to the bifurcation point filled with a leading electrolyte (LE) composed of 8 mM HCl + 16 mM β-alanine (β-Ala) + 10% PVP + 2.86 mM N₂H₄x2HCl, pH 3.2; and a terminating electrolyte composed of 8 mM H₃PO₄ + 16 mM β-Ala + 10% PVP + 5 mM N₂H₄, pH 3.85 for all the matrices except seawater. For ITP of seawater the LE consisted of 50 mM HCl + 100 mM β-Ala + 10% PVP + 2.86 mM N₂H₄x2HCl, pH 3.52. Distance of conductivity detector from the injection point and bifurcation point was 52 and 38 mm, respectively. Zone electrophoresis was performed in a capillary made of fused silica of 0.3 mm id and 160 mm total length filled with LE from isotachophoretic step. LODs reached for all matrices were 2-3x10⁻⁸ M concentration (2.5-4 μg/L) enabled monitoring of iodide in all analyzed samples with RSD 0.4-9.3%. Estimated concentrations of iodide in individual matrices were 10⁻⁶-10⁻⁸ M.
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