New electrolyte system for the determination of ammonium, alkali and alkaline earth cations by capillary electrophoresis Original Research Article

A new electrolyte system using copper(II) chelate with ethylenediamine was developed for the separation of ammonium, alkali and alkaline earth cations. In comparison with other electrolyte systems it was found to be the most favorable for the separations in alkaline medium. The optimization of the experimental parameters such as nature and concentration of counter-ion, electrolyte concentration, and pH was studied. The optimized separations were carried out in 7.5 mmol l−1 copper(II) acetate, 15 mmol l−1 ethylenediamine and 2 mmol l−1 triethanolamine at pH 8.0, with indirect UV detection at 230 nm. Eight cations (K+, NH+4, Ba2+, Sr2+, Ca2+, Na+, Mg2+ and Li+) were well separated in less than 4 min. Detection limits were in the range 5×10−6–1×10−5 mol l−1. To evaluate this system, the determination of cations was examined for mineral water and tap water samples.