Application of Capillary Electrophoresis to the Study of Equilibria on an Example of Gold(III) Complexes

Three systems of gold(III) complexes in an aqueous solution (I = 0.05 M, 25°C) with slow equilibration were studied by capillary electrophoresis. It was shown on an example of mixed chloride–hydroxide complexes Au(OH)_iCl_4-i ^- that, despite close sizes and identical charges of the forms, the mixed forms can be separated if they are kinetically inert. For the equilibria AuCl₄ ⁻+ am = AuamCl₂ ⁺ + 2Cl^– and AuamCl₂ ⁺ + am = + Auam₂ ³⁺ + 2Cl^–, where am is ethylenediamine (en) and 1,3-diaminopropane (tn), the logarithmic constants were logK₂ = 10.4 for en, and logK₁ = 16.1 and logK₂ = 12.0 for tn, which satisfactorily agrees with the spectrophotometric data. There was a considerable effect of side processes, insignificant under normal conditions.