Ion paired chromatography of iron (II,III), nickel (II) and copper (II) as their 4,7-diphenyl-1,10-phenanthroline chelates

A reversed phase ion-paired chromatographic method that can be used to determine trace amounts of iron (II,III), nickel (II) and copper (II) was developed and applied to the determination of iron (II) and iron (III) levels in natural water. The separation of these metal ions as their 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline) chelates on an Inertsil ODS column was investigated by using acetonitrile-water (80/20, v/v) containing 0.06 M perchloric acid as mobile phase and diode array spectrophotometric detection at 250-650 nm. Chromatographic parameters such as composition of mobile phase and concentration of perchloric acid in mobile phase were optimized. The calibration graphs of iron (II), nickel (II) and copper (II) ions were linear (r > 0.991) in the concentration range 0-0.5, 0-2.0 and 0 4.0 μg ml^-1 respectively. The detection limit of iron (II), nickel (II) and copper (II) were 2.67, 5.42 and 18.2 ng ml^-1 with relative standard deviation (n = 5) of 3.11. 5.81 and 7.16% at a concentration level of 10 ng ml^-1 for iron (II) and nickel (II) and 25 ng ml^-1 for copper (II), respectively. The proposed method was applied to the determination oF iron(II) and iron(III) in tap water and sea water samples without any interference from other common metal ions.