Investigation of iron(III) reduction and trace metal interferences in the determination of dissolved iron in seawater using flow injection with luminol chemiluminescence detection

Hydrogen peroxide in deep waters from the Mediterranean Sea, South Atlantic and South Pacific Oceans

“…An aged (1–2 weeks old) seawater blank accounts for the presence of stable interfering species, but not unstable interfering species such as Fe(II) and V(IV)- the concentration of which must be known at the time H 2 O 2 is measured if a correction is to be made. This difficulty arises, not only because of logistical constraints in coordinating the simultaneous measurement of multiple redox sensitive variables, but also because the measurement of Fe(II) via luminol itself is subject to a V(IV) interference36 and the chemiluminescence response of luminol to some ions, including Fe(II), is non-linear37. As an additional precaution we have therefore excluded all stations from our H 2 O 2 dataset where Fe(II) exceeded 0.3 nM at multiple depths (Fe(II) was measured at all stations in the S Atlantic and S Pacific with a detection limit of ~0.2 nM, data not shown).…”

“…Fe(II) additions were made into both low (aged, no H 2 O 2 spike) and high (aged, spiked to 42 nM) H 2 O 2 Atlantic seawater as the luminol response to some interferences may be non-linear3637. Fe(II), V(IV) and Fe(III) stock solutions were made from ammonium Fe(II) hexahydrate (99%, Sigma Aldrich), vanadyl sulfate hydrate (99.99%, Sigma Aldrich) and Fe(III) chloride hexahydrate (>99.99%, Sigma Aldrich), respectively.…”

A Comparison between Four Analytical Methods for the Measurement of Fe(II) at Nanomolar Concentrations in Coastal Seawater

“…However, it is curious that whilst the interference for V(IV) was similar for both methods, the interference from Co(II) was more pronounced for the luminol B method (Figure 2). This was unexpected as the added DMG is known to suppress this interference (Ussher et al, 2009). It was suspected that the DMG decomposed during transport as several months previously the same batch was used successfully.…”

“…The apparent Fe(II) signal arising from V(IV) was similar for both methods (Figure 2). However, the Co(II) interference was curiously greatest with the luminol B method, despite the addition of DMG to the luminol B reagent mixture to suppress Co(II) interference (Ussher et al, 2009). With the luminol A approach, the propagated standard deviation in the apparent Fe(II) concentration arising from all Co(II) spikes was large compared to the "equivalent Fe(II)" concentration measured (0.2 ± 0.1, 0.1 ± 0.1, and 0.1 ± 0.1 nM, respectively).…”

Flow-Injection Determination of Vanadium in Seawater Samples with Acidic Potassium Permanganate Chemiluminescence

“…Mn 2+ only interferes in higher (µmol L -1 range) concentrations, which are much higher than the typical coastal and shelf water Mn 2+ concentrations. 35 Equivalent amounts of Fe 2+ and Sn 2+ do not interfere, however, higher concentrations seriously interfere with the vanadium determination. The concentration of Fe 2+ and Sn 2+ in seawater is in sub-nanomolar ranges; 35,36 hence these materials have no effect when analyzing vanadium in seawater which is present in 10 -100 fold higher concentrations than Fe 2+ and Sn…”