Determination of maximum complexing ability of water-soluble complexants

Abstract

When the maximum complexing ability (MCA) of water-soluble complexants of unknown molecular weight is known, it is possible to calculate the stability constants of metal complexes where these complexants participate (2,4,5). Recently (7) MCA has been used to develop new equations which are useful in interpreting stability constants measurements made by the ion-exchange method. These equations define stability constants of anionic or zero-charge metal complexes and could be applied to soil organic matter-metal complexes. There is no general method for calculating the MCA of a complexant in solution. Several authors (2,4,5) have used different procedures, all of which were applicable only to the specific cases being studied. Therefore, the information that could be gained using the equations mentioned above would be only a function of the method used to determine MCA. MCA represents the potential complexing ability of a solution, that is, its active anionic complexing sites (7). In this paper a general method is proposed to measure MCA of water-soluble complexants that form metallic complexes of anionic or zero charge.