Determination of ferrous iron in non-refractory silicate minerals

Amonette, James E.; Scott, Alex

doi:10.1016/0009-2541(91)90077-5

Cited by 19 publications

(15 citation statements)

References 15 publications

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“…The precision of the improved method is also quite good (Table 1). Mean relative standard deviations (MRSD) between 0.5% and 0.8% were obtained, which are considerably lower than the range in MRSDs (1.6% to 3.3%) calculated for other phen datasets (Stucki 1981;E A. Khan, unpublished data) and approach the MRSD of 0.4% obtained for a precise titrimetric method (Amonette and Scott 1991). Substitution of fixed values for the digestate volume and dilution factors using the mean values obtained for all the samples in the analysis had essentially no impact on the accuracy of the method but lowered the precision by about 50%.…”

Section: Accuracy the Resultscontrasting

confidence: 62%

“…Two separate samples of MICA Fe were analyzed because preliminary runs showed the PNNL samples to yield significantly higher results for Fe(II) than expected from the reference value and previous work. To verify that the PNNL sample was indeed different, we obtained some of the MICA-Fe sample from ISU that had been used in our earlier work (Amonette and Scott 1991;F. A. Khan, unpublished data).…”

Section: Accuracy the Resultsmentioning

confidence: 99%

“…The wide range in color-development periods for photoreduction treatment (0.5 to 4 h) clearly demonstrates the need to calibrate each individual apparatus. Amonette and Scott (1991). tt Atomic absorption spectrometry, E A. Khan (unpublished data).…”

Section: -1 0 101mentioning

confidence: 99%

“…Stucki and Anderson (1981) also reported a loss in precision associated with the use of chemical reductants and slightly higher absorptivities when hydroxylamine was added to a digestate containing (nominally) only Fe(II) than when only NaCI was added. This latter result could have stemmed from Fe(III) impurities in the Fe(II) standard being reduced by the hydroxylamine rather than from any effect of the reductant, as even primary-standard-grade Fe(II) has been shown to contain Fe(III) impurities (Amonette and Scott 1991). Komadel and Stucki (1988) further refined the phen method by using a Hg-vapor lamp to reduce the Fe(III) in a matter of 90 rain, which was a significant improvement over the 36 h required when the fluorescent lamp was used.…”

Section: 10-phenanthroline Proceduresmentioning

confidence: 99%

“…Titrimetric methods rely on the reaction of redox-sensitive constituents with a known amount of oxidant or reductant and thus are not element-specific. Although they tend to be very precise (Van Loon 1965;Banerjee 1974;Amonette and Scott 1991) they also measure everything that can be oxidized or reduced by the titrant [organic matter and other transition metals such as Ti(IZI) and V0ID] and are thus best suited to measurements of overall reductive or oxidative capacity at specific formal reduction potentials. Colorimetric methods for Fe involve the specific complexation of Fe(II) or Fe(III) by a chromophore and the subsequent determination of concentration by spectrophotometry.…”

Section: Introductionmentioning

confidence: 99%

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Improvements to the Quantitative Assay of Nonrefractory Minerals for Fe(II) and Total Fe Using 1,10-Phenanthroline

Amonette

1998

Clays and clay miner.

197

116

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Abstraet--A method using 1,10-phenanthroline (phen) to quantify Fe(II) and total Fe in nonrefractory minerals was modified to improve the accuracy and precision and to eliminate the inconvenience of performing much of the analysis under darkroom conditions. Reagents were combined to minimize solution-handling errors, volumes of the reagent additions were determined gravimetrically and the acidmatrix solution was preheated to near-boiling before sample contact. The darkness requirement, which stems from the photoreduction of Fe(III) to Fe(II) in the presence of phen, was eliminated by the use of opaque amber-colored high-density-polyethylene bottles during the digestion step and for storage of the digestate and subsequent dilutions before Fe(II) analysis. Reduction of Fe(III) for total-Fe analysis was accomplished either by exposure to light from a Hg-vapor lamp or by reaction with hydroxylamine, NH2OH. Although the minimum periods required for adequate reduction ranged from 1.5 to 4 h, the optimum reduction periods were between 6 and 10 h. When standard samples containing Fe(II) and MnC12 were digested and analyzed for total-Fe using the light treatment (with incidental heating to 35-45 ~ significant decreases and in some instances, oscillations, in absorptivity were obtained. Similar experiments with NH2OH, or with CrC13 showed no effect. The absorptivity of most digestates stored in opaque bottles was stable for at least 2 weeks, although digestates with Mn concentrations above 3 ~g mL showed proportional decreases in absorptivity. Analysis of 8 geochemical reference materials by the modified method (using NH2OH) yielded excellent agreement with published values and a mean relative standard deviation of 0.6%. Total-Fe results obtained using the light treatment, however, were generally lower (-2% relative) than the NH2OH values, although this difference decreased with longer irradiation periods. Use of NH2OH was deemed preferable because it was simpler, faster, minimized interferences from Mn and eliminated the need for specialized apparatus. Lastly, MICA Fe was shown to be unreliable as a primary reference material for Fe(II) determinations.

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Section: Accuracy the Resultscontrasting

confidence: 62%

Section: Accuracy the Resultsmentioning

confidence: 99%

Section: -1 0 101mentioning

confidence: 99%

Section: 10-phenanthroline Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Improvements to the Quantitative Assay of Nonrefractory Minerals for Fe(II) and Total Fe Using 1,10-Phenanthroline

Amonette

1998

Clays and clay miner.

197

116

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WD‐XRF technique for speciation of iron and quantification of its oxidation states in geological samples using L‐series of iron X‐ray spectrum

Maurya,

Deb Barman

2024

X-Ray Spectrometry

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Wavelength dispersive X‐ray fluorescence (WD‐XRF) spectrometry is a fast and widely used technique for elemental analysis of geological samples from Na to U. However, it has seldom been applied for quantitative determination of oxidation states of elements in complex matrices. In this study, we present a method to determine the oxidation states of iron in geological samples by WD‐XRF. We used the FeLα1,2 fluorescence line as a tool for iron speciation and Fe(II)/Fetotal ratio determination. We found that the normalized intensity (peak height) of FeLα1,2 fluorescence line was linearly correlated with the spin multiplicity (2S + 1) of ferrous and ferric content in the samples. To account for the matrix effects of chemical environment (matrix and chemical bonding) on FeLα1,2 fluorescence line, we introduced a chemical index factor (μ) that enabled accurate determination of Fe(II)/Fetotal ratio in different types of geological samples. The method was validated using international certified reference materials and their mixtures and obtained promising results, with only 6 out of 55 determinations showing relative error more than 5% of the certified values.

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