A method for the determination of calcium and magnesium based on the decrease in the height of the anodic polarographic waves of ethylenediaminetetra-acetic acid (EDTA) and ethyleneglycol-bis-(β-aminoethylether)-NNN′N′-tetra-acetic acid is proposed. The sum of calcium and magnesium is determined from the height of the anodic wave of EDTA and subsequently calcium is determined on a separate aliquot from the decrease in the anodic EDTA wave.