Simultaneous Determination of Fe(III) and Fe(II) Ions via Complexation with Salicylic Acid and 1,10-Phenanthroline in Microcolumn Ion Chromatography

Fe(III) and Fe(II) ions were separated and determined via in-column and post-column reactions with salicylic acid and 1,10-phenanthroline by microcolumn ion chromatography with UV-Vis detection. The separation could be achieved on a silica microcolumn using an aqueous ethanol solution of salicylic acid as eluent. The effluent from the column was then mixed with aqueous ethanol solution of 1,10-phenanthroline and detected at 518 nm. Fe(III) ion was detected as the complex with salicylic acid, whereas Fe(II) ion was detected as the complex with 1,10-phenanthroline. The detection limits with 0.25 µL injection volume at S/N = 3 were 0.21 and 0.10 mg L-1 for Fe(III) and Fe(II), respectively. Increasing the injection volume of sample, e.g., 5.1 µL, improved the sensitivity; the detection limits at S/N = 3 were 12 and 9.2 µg L-1 for Fe(III) and Fe(II), respectively. The present system was applied to the determination of iron in a local well water sample.