The assignment of metal complexes to various regimes on the basis of their dissociation kinetics is one type of metal speciation study. The most common scheme, which involves column ion-exchange as a means of separating free metal ions and metals in the form of highly labile complexes from other forms of metals in the sample, is demonstrated to categorize incorrectly stable, charged complexes such as iron(II) and nickel(II) o-phenanthroline as labile. Donnan dialysis is an alternative ion-exchange method for metal speciation studies. Data are provided which demonstrate that the above complexes are correctly assigned by the Donnan dialysis method. The relative labilities of ethylenediamine and triethylenetetramine complexes of iron (II) and nickel (II) are also correctly determined by Donnan dialysis.