Capillary electrophoretic estimation of sulfate stability constants of metal ions and determination of alkali and alkaline earth metals in waters

We studied the influence of sulfate concentration on the effective mobilities of mono-, di- and tervalent ions and developed a method for the determination of sulfate stability constants. Relative migration times of several cations were determined. Capillary electrophoresis with indirect detection using 4 mmol/l copper(II) sulfate, 18-crown-6 and formic acid in background electrolyte was then applied to the determination of the metal ions in mineral and tap waters samples. The results were compared with those of ion chromatography. The CE detection limits were estimated [signal/noise ratio (S/N)=3] in the range from 0.59 (for Li) to 12.9 mg/l (for Ba).