Volumetric determination of iron (III) with hydroxylamine as a reducing agent

Rao, G. Gopala; Somidevamma, G.

doi:10.1007/bf00462146

Cited by 8 publications

(4 citation statements)

References 13 publications

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“…The reduction of ferric to ferrous ion is well-documented in the organic synthetic literature, and it is an essential step of colorimetric assays to determine iron concentration. 18,24,25 In contrast, N(OH) 2 -CAM is more likely to hydrolyze quickly to the NO-CAM intermediate rather than act as a reducing agent.…”

Section: ■ Resultsmentioning

confidence: 99%

“…(2) In general, hydroxylamines are efficient reducing agents for iron. The reduction of ferric to ferrous ion is well-documented in the organic synthetic literature, and it is an essential step of colorimetric assays to determine iron concentration. ,, In contrast, N(OH) 2 -CAM is more likely to hydrolyze quickly to the NO-CAM intermediate rather than act as a reducing agent. (3) The single-turnover reaction of stoichiometric NH 2 -CAM and P proceeds through NO-CAM, and NO-CAM is independently shown to react with P to form CAM.…”

Section: Discussionmentioning

confidence: 99%

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Mechanism for Six-Electron Aryl-N-Oxygenation by the Non-Heme Diiron Enzyme CmlI

Komor¹,

Rivard

Fan

et al. 2016

J. Am. Chem. Soc.

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The ultimate step in chloramphenicol (CAM) biosynthesis is a six-electron oxidation of an aryl-amine precursor (NH2-CAM) to the aryl-nitro group of CAM catalyzed by the non-heme diiron cluster-containing oxygenase CmlI. Upon exposure of the diferrous cluster to O2, CmlI forms a long-lived peroxo intermediate, P, which reacts with NH2-CAM to form CAM. Since P is capable of at most a 2-electron oxidation, the overall reaction must occur in several steps. It is unknown whether P is the oxidant in each step or whether another oxidizing species participates in the reaction. Mass spec product analysis of reactions under 18O2 show that both oxygen atoms in the nitro function of CAM derive from O2. However, when the single turnover reaction between18O2–P and NH2-CAM is carried out in an 16O2 atmosphere, CAM nitro groups contain both 18O and 16O, suggesting that P can be re-formed during the reaction sequence. Such re-formation would require reduction by a pathway intermediate, shown here to be NH(OH)-CAM. Accordingly, the aerobic reaction of NH(OH)-CAM with diferric CmlI yields P and then CAM without an external reductant. A catalytic cycle is proposed in which NH2-CAM reacts with P to form NH(OH)-CAM and diferric CmlI. Then the NH(OH)-CAM re-reduces the enzyme diiron cluster, allowing P to re-form upon O2 binding, while itself being oxidized to NO-CAM. Finally, the re-formed P oxidizes NO-CAM to CAM with incorporation of a second O2-derived oxygen atom. The complete six-electron oxidation requires only two exogenous electrons and could occur in one active site.

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Section: ■ Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Mechanism for Six-Electron Aryl-N-Oxygenation by the Non-Heme Diiron Enzyme CmlI

Komor¹,

Rivard

Fan

et al. 2016

J. Am. Chem. Soc.

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“…Hydroxylamine as a reducing agent converts the valence state of Fe ions from trivalent (Fe 3+ ) to divalent (Fe 2+ ). The reduction mechanism for Fe ions has been suggested as [Equation (1)]:

2 NH_{2} OH_{(aq)} + 4 Fe^{3 +}_{(aq)} \to N_{2} O_{(g)} + 4 Fe^{2 +}_{(aq)} + H_{2} O_{(l)} + 4 H^{+}_{(aq)}

…”

Section: Resultsmentioning

confidence: 99%

Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy

et al. 2015

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Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red–orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship between optical absorbance and Fe concentration. Many Fe catalysts were microscopically observed to be encased by graphitic layers, thus preventing their extraction. Fe catalyst dissolution from CNTs was investigated with various single and mixed acids, and Fe concentration was found to be highest with CNTs being held at reflux in HClO4/HNO3 and H2SO4/HNO3 mixtures. This novel colorimetric method to measure Fe concentrations by UV/Vis spectroscopy was validated by inductively coupled plasma optical emission spectroscopy, indicating its reliability and applicability to asses Fe content in CNTs.

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“…We used a reducing agent, 0.1 M NH 2 OH·HCl, and boiling condition [15] to treat the solution prepared from Mohr's salt, and stored the resultant standard of 1000 mg/L in an autoclaved amber glass bottle.…”

Section: Stability Of Fe(ii) and Fe(iii) Solutionsmentioning

confidence: 99%

Simultaneous Separation and Quantification of Iron and Transition Species Using LC-ICP-MS

2011

AJAC

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Using liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS), this work investigates the simultaneous separation and quantification of seven transition metal species (Fe, Mn, Co, Ni, Cu, Zn, and Cd), based on a separation scheme published by Dionex company that used the spectrophotometric method for quantification. The LC-ICP-MS method overcomes the shortcomings of conventional ferrozine approaches of measuring Fe(II) and total Fe by two separate runs and calculating Fe(III) by the difference of two runs. The advantage is particularly evident in that organo-iron species are found to be the predominant iron species in many natural waters, and the difference method cannot measure the concentration of Fe(III) because ferrozine will not complex with organo-iron species. In the work reported here, the LC-ICP-MS method is successfully applied to the separation of dissolved iron species, as well as six other divalent transition metals in tap water, deionized water, river water, hot springs, and groundwater samples.

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Volumetric determination of iron (III) with hydroxylamine as a reducing agent

Cited by 8 publications

References 13 publications

Mechanism for Six-Electron Aryl-N-Oxygenation by the Non-Heme Diiron Enzyme CmlI

Mechanism for Six-Electron Aryl-N-Oxygenation by the Non-Heme Diiron Enzyme CmlI

Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy

Simultaneous Separation and Quantification of Iron and Transition Species Using LC-ICP-MS

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