Fast analysis of water samples for detection of anions by capillary zone electrophoresis

A capillary zone electrophoresis (CZE) method with relatively low separation voltage and short capillary length, using indirect UV detection was developed for the fast and quantitative determination of Cl-, NO2-, SO4(2-), NO3-, F- and HCO3- in potable water samples. Baseline separation of inorganic and organic anions was achieved within 1 min. The optimal carrier electrolyte consisted of 6.0 mM sodium chromate, 2.5 mM CTAB and 3.5% acetonitrile at pH 9.0. The effects of pH and the concentrations of electrolyte and flow modifiers on the resolution were investigated. Two injection methods, gravity and electrokinetic, were compared. The application of electrokinetic injection, using pyroglutamic acid as an internal standard was found to provide a method that is fast, sensitive and quantitative, with an R.S.D. for migration times from 0.1% to 0.3% and for peak areas from 1.8% to 4.1%. The limits of detection were 0.08 mg/L Cl-, 0.3 mg/L NO2-, 0.1 mg/L SO4(2-), 0.1 mg/L NO3-, 0.07 mg/L F-, and 0.3 mg/L HCO3-. This method has been successfully applied to determine Cl-, NO2-, SO4(2-), NO3-, F-, HCO3- in municipal water, surface water and bottled water samples.