More sensitive way to determine iron using an iron(II)-1,10-phenanthroline complex and capillary electrophoresis

Iron is one of the major metal species of concern in many samples, such as in serum, foods, drinking waters, etc. In this paper, we present a more sensitive way to determine the iron concentration in water solutions by using an iron(II)-1,10-phenanthroline complexing system with high-performance capillary electrophoresis, and have applied this method to the determination of the levels of iron in serum samples. The technique uses ammonium acetate-acetic acid (50 mM NH4Ac-HAc, pH 5.0) as a running buffer, and the detection wavelength is set at 270 nm instead of 508 nm. This new approach enhances the molar absorbance of the Fe(II)-1,10-phenanthroline complex by about eight-fold compared with that obtained at 508 nm. By combining the larger light output of the deuterium (D2) lamp and the lower noise level at 270 nm, the sensitivity was improved at least twenty-fold compared to that at 508 nm. The detection limit for iron(II) is lower than 5 x 10(-9) M, which has never been reached by reported spectrophotometric methods or with the recently published HPCE method. The effects of pH, buffer concentration and operation voltages on the sensitivity and resolution are also discussed. The signal response is linear over two orders of magnitude (r2 = 0.995) and the iron recovery for samples reached 99-101%. The technique described here is much more sensitive, fast and simple and is suitable for determining trace amounts of iron in biological, food, water and other samples.