Simultaneous determination of nitrate and nitrite ions in seawater by capillary zone electrophoresis using artificial seawater as the carrier solution

Abstract

We are proposing a novel capillary zone electrophoresis for the simultaneous determination of nitrate and nitrite ions in seawater. An artificial seawater was adopted as the carrier solution to eliminate the interference of high concentrations of chloride ion etc., in seawater. For the purpose of reversing the electroosmotic flow, 3 m M cetyltrimethylammonium chloride was added to the carrier solution. A 100 μm I.D. capillary was used to extend the optical path length. Regardless of the salinity of sample solutions, the peak areas and migration times for nitrate and nitrite ions were within ±3%, while the peak heights for these ions decreased linearly with increasing salinity of sample solutions. The limits of detection for nitrate and nitrite ions were 0.04 and 0.07 mg/l ( S/ N=3, based on three-times the baseline noise), respectively. The values of the relative standard deviation (RSD) of peak areas for these ions were 1.5 and 2.4%. The RSDs of migration time for these ions were 0.85 and 0.78%. The proposed method was applied to the determination of nitrate and nitrite ions in seawater samples taken from the surface and the seabed. The recovery of nitrate and nitrite ions was 97–114%.