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

We are proposing a novel capillary zone electrophoresis for the simultaneou s determination of nitrate and nitrite ions in seawater. An artificial seaw ater was adopted as the carrier solution to eliminate the interference of h igh concentrations of chloride ion etc., in seawater. For the purpose of re versing the electroosmotic Bow, 3 mM cetyltrimethylammonium chloride was ad ded to the carrier solution. A 100 mu m I.D. capillary was used to extend t he 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 increasi ng salinity of sample solutions. The limits of detection for nitrate and ni trite ions were 0.04 and 0.07 mg/l (S/N=3, based on three-times the baselin e 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 t he surface and the seabed. The recovery of nitrate and nitrite ions was 97- 114%. (C) 1999 Elsevier Science B.V. All rights reserved.