In situ speciation of trace Fe(II) and Fe(III) in atmospheric waters by the FZ method coupled to GFAAS analysis

Abstract : A quasi-on-line method of measurement of the oxidation states of iron coupled with a GFAAS analysis is reported for the trace conditions found in atmospheric waters. This technique is based on the formation of a specific complex [Fe(FZ)3](4-) between Fe(II) and ferrozine (FZ). tC(18) solid-phase extraction cartridges (Sep-Pak) are used to separate the [Fe(FZ)3](4-) and Fe(III) so as to limit the risk of redox evolution of the sample. The adaptation to dilute aqueous media, via acidification at pH 2 of rainwater sample, and atmospheric interferences are discussed, and the Fe(II) recovery in rainwaters is determined. This method coupled with a quasi-on-line sampling protocol has been tested on rains collected in Guadeloupe Island (Caribbean Sea, 16 degrees N, 61 degrees W) during a field campaign in May 2005. Our results show that the proposed method can satisfactorily be applied to the determination of Fe(II) and Fe(III) in atmospheric waters under in situ conditions.