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) i Cl 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 AuCl 4 − + am = AuamCl 2 + + 2Cl – and AuamCl 2 + + am = + Auam 2 3+ + 2Cl – , where am is ethylenediamine (en) and 1,3-diaminopropane (tn), the logarithmic constants were log K 2 = 10.4 for en, and log K 1 = 16.1 and log K 2 = 12.0 for tn, which satisfactorily agrees with the spectrophotometric data. There was a considerable effect of side processes, insignificant under normal conditions.