Capillary electrophoretic separation of metal ions in the presence of polyethylene glycols

Abstract

The capillary electrophoretic separation of the metal ions lithium, potassium, magnesium, barium, zinc, lead, lanthanum, samarium, europium and dysprosium was examined in the presence of polyethylene glycol additives (0.01–10%) having relative molecular masses between 200 and 20 000 000 g mol l^–1. Changes observed in electrophoretic mobilities, separation selectivity, resolution and electroosmotic flow depended on the relative molecular mass and concentration of the polyethylene glycol. Decreases in electrophoretic mobility (e.g., 45% for lithium) were attributed to polyethylene glycol–metal ion interactions. For the higher molecular mass polymers ( 20 000 g mol l^–1), concentrations greater than about 1% m/v were found to have a detrimental effect on detection sensitivity and separation current stability, presumably owing to aggregate formation. Efficiencies were in the range 120 000–260 000 theoretical plates, and applications to the analysis of a fermentation broth and an aqueous soil extract sample were examined.