Simultaneous Separation and Quantification of Iron and Transition Species Using LC-ICP-MS

Qinhong Hu

doi:10.4236/ajac.2011.26077

Abstract

Using liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS), this work investigates the simultaneous separation and quantification of seven transition metal species (Fe, Mn, Co, Ni, Cu, Zn, and Cd), based on a separation scheme published by Dionex company that used the spectrophotometric method for quantification. The LC-ICP-MS method overcomes the shortcomings of conventional ferrozine approaches of measuring Fe(II) and total Fe by two separate runs and calculating Fe(III) by the difference of two runs. The advantage is particularly evident in that organo-iron species are found to be the predominant iron species in many natural waters, and the difference method cannot measure the concentration of Fe(III) because ferrozine will not complex with organo-iron species. In the work reported here, the LC-ICP-MS method is successfully applied to the separation of dissolved iron species, as well as six other divalent transition metals in tap water, deionized water, river water, hot springs, and groundwater samples.

Highlights

Concentration determination of soluble reactive species is key to understanding biogeochemical processes in aquatic and terrestrial environments
Using liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS), this work investigates the simultaneous separation and quantification of seven transition metal species (Fe, Mn, Co, Ni, Cu, Zn, and Cd), based on a separation scheme published by Dionex company that used the spectrophotometric method for quantification
The LC-ICP-MS method overcomes the shortcomings of conventional ferrozine approaches of measuring Fe(II) and total Fe by two separate runs and calculating Fe(III) by the difference of two runs

Summary

Introduction

Concentration determination of soluble reactive species is key to understanding biogeochemical processes in aquatic and terrestrial environments. Iron is present in the hydrosphere under two oxidation states, Fe(II) and Fe(III), which are thermodynamically stable under anoxic and oxic conditions, respectively [5]. Measurements of both dissolved Fe(II) and Fe(III) concentration are important in assessing iron’s contribution in mediating numerous biogeochemical processes that involves many elements [6]. When Fe(III) is present in the aqueous samples, either as a true dissolved complex or in colloids, a separate reduction step with hydroxylamine (NH4OH·HCl) is performed to measure the total iron, with the difference ascribed to Fe(III) [5,6]. The approach lacks sufficient sensitivity for determining iron concentrations in natural waters at μg/L levels, and a pre-concentration is usually required

Methods

Results

Conclusion