Simultaneous determination of iron(II) and iron(III) in water by capillary electrophoresis

Capillary zone electrophoresis (CZE) was applied for the simultaneous determination of iron(II) and iron(III) selectively complexed with 1,10-phenanthroline and CDTA. The best separation was achieved using a fused silica capillary (47 cm × 75 μm i.d.) filled with a borate buffer (100 mmol l−1, pH 9.0) and with direct UV detection at 254 nm. The separation time is less than 3 min. The influence of different experimental parameters such as pH, the sequence of adding and the molar ratio of the complexing agents on the iron(II)/iron(III) ratio was studied. The complexed sample mixture (pH 9.0) is stable for a few days at room temperature. The detection limits achieved are 0.06 mg l−1 for Fe(II) and 0.1 mg l−1 for Fe(III). The method was applied for the determination of both dissolved iron species in tap water and groundwater samples.