EDTA, ethylenediaminetetraacetic acid, is a common chelating agent used widely in industrial products. It finds utility in peroxide (chlorine-free) bleaching in pulp and paper applications, as a dye stabilizer in the textile industry, as a food stabilizer, and in medicinal chelation therapy. While EDTA is highly effective and generally considered safe, it is not readily biodegradable. The widespread use of EDTA has led to its classification as a persistent organic pollutant.

Industry has developed several potential substitutes for EDTA. Specifically, EDDS, ethylenediaminedisuccinate, is an isomer of EDTA and is finding increasing use in cleaning products, for example. The S,S stereoisomer is especially biodegradable. These reagents, however, have not found their way into the analytical laboratory. One of the most common analyses is the determination of water hardness via titration with EDTA and eriochrome black indicator. We have compared the determination of water hardness using EDDS as the titrant to identical analysis with EDTA. Our experiments with aqueous standards of Ca2+ and tap water show these greener alternatives as comparable to EDTA. On the other hand, we obtained low results with standard solutions of Mg2+. We are investigating binding constants to determine this discrepancy. Meanwhile, we have compared EDTA and EDDS for the water hardness titration as performed in our general chemistry laboratory. Other complexation reactions are also underway. Hence, green alternatives to the use of a common analytical reagent exist.