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 Fe[HEDTA], Fe[EDTA](1-) and Fe[DTPA](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 (40)Ar(16)O(+) interference in the detection of (56)Fe via the addition of either H(2) 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 (NH(4))(2)HPO(4) at pH 8.0, but only Fe[HEDTA], Fe[EDTA](1-) and Fe[DTPA](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.