Sensitive and selective method for direct determination of nitrite and nitrate by high-performance capillary electrophoresis

In this paper a sensitive and selective method for the direct determination of nitrite and nitrate by highperformance capillary electrophoresis (HPCE) is described. Separation conditions are optimized using a statistic orthogonal design. Optimization results suggest that the effects of several experiment factors on the separation follow the order: cetyltrimethylammonium bromide (CTAB) concentration > buffer pH approximate to buffer concentration > run voltage. The results also suggest that better separation could be achieved at relatively low electric field (10 kV/50 cm). Nitrite, nitrate, and bromide (an internal standard) are well separated in the optimized buffer 20 mmol/l of tetraborate plus 1.1 mmol/l of cetyltrimethylammonium chloride (CTAC). HPCE separation at a CTAC concentration of 1.1 mmol/l is considered to involve an ion-pair association mechanism. The specificity and quantitation-including calibration range, reproducibility, and minimum detection limit are examined. Finally, the method was used to analyze samples such as tap or river water, a large amount of nitrate in the water does not interfere with the determination of a small amount of spiked nitrite.