New electrolyte composition for determination of anions by capillary electrophoresis with indirect UV detection

This paper proposes a new analytical method by capillary electrophoresis (CE) with indirect UV detection for determining the following anions: fluoride, chloride, bromide, nitrite, nitrate, sulphate and phosphate in water, biological fluids, or other similar media. Various substances were tried to perform the functions of background electrolyte and electro-osmotic flow (EOF) modifier. In addition, a study was undertaken of the influence over the analytical parameters of anions of variation in the main factors affecting the electrophoretic process, such as: concentration of background electrolyte and EOF modifier, pH of electrolyte, voltage, and temperature. The data obtained from this work allow the most appropriate conditions for the analysis of these anions to be fixed. These are: EOF modifier: benzethonium chloride 0.10 mM; background electrolyte: sodium thiosulphate 25.0 mM; pH = 5.00; voltage 15.0 kV; and T = 25degreesC. Under these conditions, analyses can be performed of all the anions listed, in times ranging from 3.72 min for bromide to 5.30 min for phosphate, with detection limits lying between 0.12 mug/mL for fluoride and 0.35 mug/mL for nitrite.