Large-volume sample stacking in acidic buffer for analysis of small organic and inorganic anions by capillary electrophoresis

This paper describes a straightforward approach for stacking extremely large volumes of sample solutions containing small organic and inorganic anions in capillary electrophoresis. The methodology involves the stacking of large sample volumes and the separation of the stacked anions in an acidic buffer (pH <4) without intermediate polarity switching. More than 300-fold enrichment was readily attained in a few minutes in the stacking of two similar organic (maleic and fumaric acids) and two inorganic (bromide and nitrate) anions. The applicability of the technique was tested in the determination of trace amounts of nitrate anion (analyte-to-matrix ratio being 1:2 x 10(4) and 1:2.5 x 10(6)) in analytical-grade potassium bromide and boric acid.