Determination of inorganic ions in ethanol fuel by capillary electrophoresis

the control of the content of inorganic ions in vehicular fuels plays an important role in the engine maintenance. a novel and versatile methodology to carry out rapid analysis of ions in ethanol is presented. capillary electrophoresis was used to quantify cations (sodium, potassium, calcium, magnesium, and ammonium) and anions (sulfate, chloride, and nitrate). the injection of the sample directly in the capillary shows some lack of repeatability of the results. the prior evaporation of the ethanol, followed by a re-suspension of the residual material, leads to reliable results. the detection limits of the eight ions range between 0.06 and 0.18 mg l-1. lower detection limits could be attained by increasing the injection time and/or the injection pressure.