Estimation of Small Stability Constants in Aqueous Solution. The Chromium(III) Chloride System.

Bjerrum, Morten J.; Bjerrum, Jannik; Grjotheim, K.; Vilkov, L. V.; Volden, Hans V.; Maartmann-Moe, Knut; Wold, Svante

doi:10.3891/acta.chem.scand.44-0358

Cited by 16 publications

(29 citation statements)

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“…3f–j). The strong bonds associated with chlorinated Cr complexes results in efficient Cr(III)-Cl complexation with Cl-coordination number increasing with HCl concentration [34]. Fig.…”

Section: Resultsmentioning

confidence: 99%

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Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis

Larsen

Wielandt

Schiller

et al. 2016

Journal of Chromatography A

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Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of these species can result in incomplete Cr recovery during chromatographic purification. Because of large mass-dependent inter-species isotope fractionation, incomplete recovery can affect the accuracy of high-precision Cr isotope analysis. Here, we demonstrate widely differing cation distribution coefficients of Cr(III)-species (Cr(3+), CrCl(2+) and CrCl2(+)) with equilibrium mass-dependent isotope fractionation spanning a range of ∼1‰/amu and consistent with theory. The heaviest isotopes partition into Cr(3+), intermediates in CrCl(2+) and the lightest in CrCl2(+)/CrCl3°. Thus, for a typical reported loss of ∼25% Cr (in the form of Cr(3+)) through chromatographic purification, this translates into 185 ppm/amu offset in the stable Cr isotope ratio of the residual sample. Depending on the validity of the mass-bias correction during isotope analysis, this further results in artificial mass-independent effects in the mass-bias corrected (53)Cr/(52)Cr (μ(53)Cr* of 5.2 ppm) and (54)Cr/(52)Cr (μ(54)Cr* of 13.5 ppm) components used to infer chronometric and nucleosynthetic information in meteorites. To mitigate these fractionation effects, we developed strategic chemical sample pre-treatment procedures that ensure high and reproducible Cr recovery. This is achieved either through 1) effective promotion of Cr(3+) by >5 days exposure to HNO3H2O2 solutions at room temperature, resulting in >∼98% Cr recovery for most types of sample matrices tested using a cationic chromatographic retention strategy, or 2) formation of Cr(III)-Cl complexes through exposure to concentrated HCl at high temperature (>120 °C) for several hours, resulting in >97.5% Cr recovery using a chromatographic elution strategy that takes advantage of the slow reaction kinetics of de-chlorination of Cr in dilute HCl at room temperature. These procedures significantly improve cation chromatographic purification of Cr over previous methods and allow for high-purity Cr isotope analysis with a total recovery of >95%.

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“…3f–j). The strong bonds associated with chlorinated Cr complexes results in efficient Cr(III)-Cl complexation with Cl-coordination number increasing with HCl concentration [34]. Fig.…”

Section: Resultsmentioning

confidence: 99%

“…3). Hence, the isotope composition of each Cr(III)-specie changes with variation in their relative abundance, as well as through chemical equilibration, which is known to be extremely slow for Cr(III)-Cl complexation at room temperature [34,35].…”

Section: Inter-species and Intra-peak Cr Isotope Fractionationmentioning

confidence: 99%

Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis

Larsen

Wielandt

Schiller

et al. 2016

Journal of Chromatography A

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“…The stability constants have been reported to be as functions of water activity (a H2O ) and mean activity of a chloride salt, LiCl ( c AE ). 14) Since our experimental system is HCl system, from a correlation 15) a maximum point at 8.0-8.5 M HCl, and decreases at the higher acidity region. We now discuss this acidity dependence.…”

Section: Resultsmentioning

confidence: 99%

“…From the reported stability constants (apparent stability constants) 14) for reactions 1 to 4, mole fractions of Cr species were estimated as functions of [HCl] (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

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Mass-Independent Isotope Fractionation in the Chemical Exchange Reaction of Chromium (III) Using a Crown Ether

Fujii

Moynier

Yin

et al. 2008

Journal of Nuclear Science and Technology

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Chromium isotopes were fractionated in a liquid-liquid extraction system using dycycrohexano-18-crown-6 at various hydrochloric acid concentrations. The isotopic ratios of 50 Cr/ 52 Cr and 53 Cr/ 52 Cr were measured precisely by the multi-collector inductively coupled plasma spectrometry (MC-ICP-MS). The isotope enrichment factor for 50 Cr-52 Cr isotope pair was shown to vary between 1:5$2:3‰ and changed as a function of acidity. The magnitudes of mass-independent isotope fractionation could be attributed to the nuclear field shift effect.

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Windowless cell for fourier transform Raman spectra of liquids and aqueous solutions

Brooker

Nielsen

Christensen

1995

J Raman Spectroscopy

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Fourier transform (FT) Raman spectra were obtained for water and aqueous solutions in a stainless-steel, windowless, liquid captive cell of simple design. It was demonstrated that high-quality Raman spectra in the lowwavenumber region (down to 100 cm-') can be obtained from highly colored samples without the presence of interfering bands from the usual sample containers made of glass or plastic. Raman bands at 520 and 232 cm-' due to the symmetric stretching modes of the Cr-0 vibration of the Cr(H,O):+ and the Cr-Cl vibration of the CrCli-complexes were observed for very dark samples that are not amenable to conventional Raman techniques. FT-Raman studies of aqueous Cr(II1) solutions can provide valuable information on the slow ligand exchange rates.

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Estimation of Small Stability Constants in Aqueous Solution. The Chromium(III) Chloride System.

Cited by 16 publications

References 0 publications

Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis

Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis

Mass-Independent Isotope Fractionation in the Chemical Exchange Reaction of Chromium (III) Using a Crown Ether

Windowless cell for fourier transform Raman spectra of liquids and aqueous solutions

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