Introduction to uses of EDTA

JSGT 1959 V43 T030-T036

The analytical uses of ethylenediamine tetra-acetic acid (EDTA) are reviewed. These uses arise from the ability of EDTA to form highly stable complex compounds with almost all metals. The main analytical use of EDTA is 'complex metric titration' in which a metal is determined by titration with EDTA solution; more than forty metals can be determined in this manner. Choice of pH of solution, or use of selective precipitating or complexing agents, often permits titration of one metal in a mixture of metals. Such methods are rapid where they avoid need for separations and where they can replace gravimetric methods. In glass analysis complexometric titration of Ca, Mg, Ba, Al, Zn, and Pb are of proved or potential value. EDTA has also been used extensively as a masking agent to improve the selectivity of various analytical reactions by inhibiting interfering metals. Examples quoted include determination of Mo, W, U, Be, Ca, Ba, K, Cu, sulphate, and borate. Several such applications are relevant to problems in glass analysis. The third main analytical use of EDTA relates to its effect on oxidation–reduction equilibria, principally in polarography.

H. J. Cluley