Separation of alkali and alkaline-earth metal and ammonium cations by capillary electrophoresis using poly(ethylene glycol) and tartaric acid

The separation behavior of alkali and alkaline-earth metal and ammonium cations was investigated by capillary electrophoresis (CE) using poly(ethylene glycol) (PEG) and tartaric acid (H(2)Tar) as electrolyte systems. Creatinine was used as a visualized co-ion for indirect UV detection (254 nm). Separation of all the analyte cations increased with the volume fraction of PEG in water and the decrease in mobility for alkaline-earth metal cations was larger than that for alkali metal cations. The separation of alkaline-earth metal cations was also enhanced by complex formation with tartarate ions, resulting in decreased mobility. Addition of H(2)Tar in water-PEG (50:50, v/v) had a larger effect than addition to water alone, suggesting larger stability constants with alkaline-earth metal cations. The separation pattern of alkaline-earth metal cations by H(2)Tar in water was in good agreement with the results calculated. Thus, the group separation of monovalent and divalent cations, respectively, and also the complete separation of all cations were shown for the electrolyte systems of PEG and H(2)Tar.