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

We describe capillary zone electrophoresis (CZE) for the simultaneous deter mination of bromide, nitrite and nitrate ions in seawater. Artificial seawa ter was adopted as the carrier solution to eliminate the interference of hi gh concentrations of salts in seawater. The artificial seawater was free fr om bromide ion to enable the determination of bromide ion in a sample solut ion. For the purpose of reversing the electroosmotic flow (EOF), 3 mM cetyl trimethylammonium chloride (CTAC) was added to the carrier solution. A 100 mu m ID (inside diameter) capillary was used to extend the optical path len gth. The limits of detection (LODs) for bromide, nitrite, and nitrate ions were 0.46, 0.072, and 0.042 mg/L (as nitrogen), respectively. The LODs were obtained at a signal to noise ratio (S/N) of 3. The values of the relative standard deviation (RSD) of peak area for these ions were 1.1, 1.5, and 0. 97%. The RSDs of migration time for these ions were 0.61, 0.69, and 0.66%. Artificial seawater samples containing various concentrations of bromide, n itrite, and nitrate ions were analyzed try the method. The error was less t han +/-12% even if the concentration ratio of bromide ion to nitrite or nit rate ion was 20-240. The proposed method was applied to the determination o f bromide, nitrite, and nitrate ions in seawater samples taken from the sur face and the seabed. These ions in other environmental waters such as river water and rainwater samples were also determined by ion chromatography (IC ) as well as this method.