Amperometric titration of calcium,strontium and barium and their mixtures in presence of large amounts of alkali metal salts

Trace amounts of alkaline earth metals are titrated with triethylenetetraaminehexaacetic acid; lead(II) is added as indicator and the current is measured by square-wave polarography. At pH 13.3, calcium, strontium and barium give a common end-point corresponding to the total content of alkaline earth ions. Copper and cadmium interfere but small concentrations of Ni, Al, Mg, Zn, Mn(II) and Fe(III) are tolerated. The alkaline earth metals can be determined in the presence of 1000-fold amounts of lithium and 10⁵- fold amounts of sodium or potassium ions.