Simultaneous determination of inorganic anions and cations in waters by capillary electrophoresis

The applicability of a recently proposed capillary electrophoresis technique based on the electromigrative sample introduction from both ends of the capillary was further investigated for the simultaneous determination of inorganic anions and cations in real water samples. The optimized separations were carried out in 5.0 mmol l-1 copper(II)-ethylenediaminehydroxide and 2.0 mmol l-1 triethanolamine electrolyte neutralized with chromic acid to pH 8.0, using indirect UV detection at 254 nm. Nine inorganic ions (Cl-, NO3-, SO4(2-), HCO3-, K+, NH4+, Na+, Ca2+ and Mg2+) were well separated in less than 5 min. The analytical performance of the method is discussed in terms of migration time, peak area and corrected peak area repeatability, linearity of response and detection limits. To evaluate this system, the determination of anions and cations was examined for mineral water, tap water and river water samples using Li+ as the internal standard. The comparison of the results with ion chromatography and conventional capillary electrophoresis is presented.