| Abstract
| - The effects of dissolved organic compounds on the determination of nanomolar concentrations of Fe(II) have beencompared using two luminol-based flow injection chemiluminescence (FI-CL) methods. One used the directinjection of sample into the luminol reagent stream, andthe other incorporated on-line solid-phase extraction ofthe analyte on an 8-hydroxyquinoline microcolumn. TheCL signals from analyses of dissolved iron species (Fe(II) and Fe(III)) with model ligands and organic compounds were examined in high-purity water and seawater.The organic compounds included natural reducing agents(e.g., ascorbic acid), nitrogen σ-donor/π-acceptor compounds (e.g., 1,4-dipyridine, protoporphyrin IX), aromatic compounds (e.g., 1,4-dihydroxybenzene), syntheticiron chelators (e.g., EDTA), and natural iron bindingcompounds (e.g., desferrioxamine B, ferrichrome A). Fe(II) determinations for both luminol FI-CL methods wereaffected by submicromolar concentrations of redox-activecompounds, strong iron binding ligands (i.e., log KFeL>6), and compounds with electron-donating functionalgroups in both high-purity water and seawater. This wasdue to reactions between organic molecules and ironspecies before and during analysis, rather than chemiluminescence caused by the individual organic compounds.In addition, the effects of strong ligands and size speciation on Fe(II) recoveries from seawater following acidification (pH 2) and reduction (100 μM sodium sulfite) wereinvestigated.
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