Identification of Fe‐polycarboxylic complexes by electrospray ionization mass spectrometry and reduction of interferences by ion chromatography/inductively coupled plasma mass spectrometry with an octopole reaction system

Stable complexes are required during the ion chromatographic (IC) separation of Fe‐polycarboxylic acid complexes. Electrospray ionization mass spectrometry (ESI‐MS) was used to identify 1:1 stoichiometric complexes of FeHEDTA], FeEDTA]^1? and FeDTPA]^2?, and the spectra showed that these Fe complexes were stable in solution. Furthermore, inductively coupled plasma mass spectrometry (ICP‐MS) using an octopole reaction system (ORS) reduced polyatomic ion ⁴⁰Ar¹⁶O⁺ interference in the detection of ⁵⁶Fe via the addition of either H₂ or He to the ORS, with He at a flow rate 3.5 mL min^?1 being the optimum collision gas. Finally, IC/ICP‐MS was used for the separation and detection of Fe complexes with an eluent containing 30 mM (NH₄)₂HPO₄ at pH 8.0, but only FeHEDTA], FeEDTA]^1? and FeDTPA]^2? were observed within 10 min with reasonable resolution. Detection limits in the range of 10–13 µg L^?1 were achieved using He as the collision gas. The proposed method was used for the determination of Fe species in soil solutions. Copyright © 2010 John Wiley & Sons, Ltd.