For the first time, the study describes the potentialities of a powerful preconcentration technique called fieldenhanced
sample injection (FESI) combined with water-in-oil microemulsion electrokinetic chromatography (W/O
MEEKC) for the quantification of inorganic anions. Water-in-oil microemulsions as background electrolytes show unique
selectivities of W/O MEEKC compared to the standard capillary-electrophoresis analysis of anions. The effect of a set of
microemulsion parameters such as the concentration and type of the buffer solution, oil, and surfactant was attained using
the separation of the test mixture. The combination of the FESI technique followed by optimized W/O MEEKC provided
up to a 930-fold improvement in the detection sensitivity compared to the conventional sample injection. The potential of
the developed method was demonstrated by the determination of iodide anions in hen eggs.
Keywords: Capillary electrophoresis, field-enhanced sample injection, food analysis, hen egg, inorganic anions, iodide, microemulsion
electrokinetic chromatography, normal stacking mode, on-line preconcentration, sample stacking, water-in-oil microemulsion.
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