DIRECT DETERMINATION OF IRON(II), IRON(III) AND TOTAL IRON AS UV-ABSORBING COMPLEXES BY CAPILLARY ELECTROPHORESIS

Capillary electrophoresis (CE) was investigated for the separation of iron(II) and iron(III) after selective complexation of these species b y o-phenanthroline and EDTA added in excess to the sample solution. Th e cationic and anionic natures of the ferrous and ferric complexes, re spectively, allow their easy electrophoretic analysis in a single run in the presence of an electro-osmotic flow. It was ascertained that th e addition of the mixed complexing solution does not alter the iron(II )/iron(III) ratio of the sample and no significant evolution of this r atio was observed over a period of ten days. Using direct UV absorbanc e detection, the developed method allows the simultaneous determinatio n of iron(II) and iron(III) in less than 3 min with R.S.D.<1% for migr ation times and <3.5% for corrected peak areas. Excellent detection li nearity was also obtained. When only EDTA is added as complexing agent , CE allows the rapid direct determination of total iron content, whic h provides a means for checking total iron recovery. Both methods were successfully applied to monitor a wet chemistry process converting ir on(II) into iron(III).