Investigation of UV-Induced decomposition of hexacyanoferrate(II) and -(III) by capillary electrophoresis

UV-degradation processes of hexacyanoferrate(II) and hexacyanoferrate(III) in aqueous solutions were studied using capillary electrophoresis (CE). A variety of solutions were UV irradiated. In each case an intermediate appears, aquapentacyanoferrate(II) and aquapentacyanoferrate(III), respectively. The polycyanoferrate species were separated using 30 mM phosphate buffers with different pHs and applying negative voltage. They were identified by synthetic standards. The migration time of aquapentacyanoferrate(II) was 7.6 min at pH=12, while aquapentacyanoferrate(III) migrated after 6.8 min at pH= 10. Concentration profiles of polycyanoferrates were constructed from the CE electrophorograms of the appropriate aliquots sampled at regular intervals. The final products of photolytic degradation depend on the pH of the solutions, producing Prussian blue in acidic media, and hydrated iron oxides and cyanides in alkaline media.