Optimization of Conditions for the Determination of Low Concentrations of Chlorate Ions in Alkali Metal Chloride Solutions by Capillary Electrophoresis.

The separation of chloride and chlorate ions in the case of a significant excess of chloride ions in a sample is studied by capillary electrophoresis. It is found that under standard separation conditions using a chromate background electrolyte, the signal-to-noise ratio for the chlorate ion peak at c() = 0.1 mM sharply decreases at the concentration ratio c(Cl–)/c() > 100. A number of approaches are considered to eliminate this phenomenon. The most effective approach was to introduce a solution containing acetate ions into the capillary after the sample zone to create conditions for transient isotachophoresis. Optimal parameters for the electrophoretic separation of chloride and chlorate ions are selected at a chloride ion content of 35 mM in the sample. The limit of detection is 0.01 mM chlorate ions (0.03−0.06% based on the mass of dry potassium, sodium, or lithium chlorides). The calibration curve is linear in the range of 0.01−1 mM . The selected conditions allow the determination of chlorate ions at a molar ratio of chloride to chlorate ions of 35−3500. The stacking efficiency factors are 10−70. Perchlorate ions do not interfere with the determination of chlorate ions at the concentrations of both ions of 0.1 mM or lower. The procedure is tested by analysis of table salt. [ABSTRACT FROM AUTHOR]