Improvement of capillary zone electrophoresis sensitivity with artificial seawater as the background electrolyte utilizing transient isotachophoresisfor the determination of nitrite and nitrate ions in seawater

We describe capillary zone electrophoresis (CZE) with transient isotachopho resis (ITP) for the determination of low concentrations of nitrite and nitr ate ions in seawater. Bromide-free artificial seawater was adopted as backg round electrolyte (BGE) to eliminate the interference of high concentration s of salts in seawater. To reverse the electroosmotic flow (EOF), 3 mM cety ltrimethylammonium chloride (CTAC) was added to the BGE. High concentration s of chlorate were added to sample solutions as the terminting ion to gener ate the ITP process before the CZE separation. In general, the stacking eff ect increased with increasing amounts of chlorate injected into the capilla ry. The limits of detection (LODs) for nitrite and nitrate were 0.063 and 0 .033 mg/L when the chlorate concentration was 600 and 200 mM, respectively; these were half of those obtained by CZE without the transient ITP. The LO Ds were obtained at a signal to noise ratio (S/N) of 3. The relative standa rd deviations (RSD, n = 10) of the peak areas for these ions were 3.2 and 2 .9%. The RSDs of peak heights for these ions were 1.6 and 2.1%. The RSDs of migration times for these ions were 0.67 and 0.46%.