Column chromatographic speciation of chromium for Cr(VI) and several species of Cr(III)

Collins, Kenneth E.; Bonato, Pierina Sueli; Archundia, C.; Queiroz, Maria Eliana Lopes Ribeiro de

doi:10.1007/bf02268143

Cited by 37 publications

(15 citation statements)

References 18 publications

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“…Cr(VI) is only present in solutions with sufficiently low hydrochloric acid molarity (<0.1 M HCl) and at >120 °C. The identity of the hydrated Cr(III)-species, Cr(H 2 O) 4 Cl 2 + , Cr(H 2 O) 5 Cl 2+ and Cr(H 2 O) 6 3+ , was verified by radiometric gamma ray counting on 51 Cr in HCl solutions [10,35]. In addition to these species, a neutral Cr(III)-Cl complex, interpreted as Cr(H 2 O) 3 Cl 3 °, was identified in Cr solutions reacted with concentrated hydrochloric acid (e.g.…”

Section: Resultsmentioning

confidence: 99%

“…Here we focus on the chemical purification procedures required for accurate and reproducible TIMS and MC-ICP-MS analysis. Quantitative separation of high purity Cr for high-precision isotope analysis is complicated by the potential presence of multiple Cr-hydration, oxidation complexes and Cr-ligand species [10]. Differences in the effective charge and radius of these complexes results in varying selectivity during ion exchange reactions, while the generally sluggish reaction kinetics of Cr-ligand complexation makes a quantitative evaluation of their relative abundances unpredictable.…”

Section: Introductionmentioning

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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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

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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“…Based on the aquation results, it is concluded that the neutral species produced by the reduction reaction is The identities of these species were made by comparison to the chromatographic behavior of species of similar charge found by cation exchange determinations of aqueous solutions of CrCl 3 [21]. The results show that following reduction of CrO 3 in concentrated hydrochloric acid, the formation of chromium-chloride complexes takes place and that these complexes can be characterized by chromatographic methods.…”

Section: Resultsmentioning

confidence: 99%

A radiochromatograpic study of the reaction of ⁵¹CrO₃ with hydrochloric acid

Pezzin¹,

Collins²

2001

Radiochimica Acta

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The objective of the present work is to verify the reduction of CrO 3 in concentrated hydrochloric acid, using 51 Cr as a tracer. For the study, 51 CrO 3 was added to 37% HCl and maintained under agitation at 20 • C for specified time periods. Aliquots were diluted to approximately pH 2 and analyzed by open column cation and anion chromatography, either immediately or after storage for specified time periods. The separations, which were made by stepwise elution using HClO 4 and Ca(ClO 4 ) 2 solutions as eluents with fraction collection, followed by counting with a NaI(Tl) detector and a single channel analyzer, permitted construction of elution profiles whose peaks were identified by comparison with authentic samples. The results show that CrO 3 is reduced to Cr(III) in 37% HCl and that the initial identifiable product is [CrCl 3 (H 2 O) 3 ], a product which undergoes slow aquation at pH 2 to [Cr(H 2 O) 4 Cl 2 ] + , [Cr(H 2 O) 5 Cl] 2+ and [Cr(H 2 O) 6 ] 3+ .

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“…(EG&G Ortec 918) radionuclidic analysis which utilized the 0.320 MeV peak of 51 Cr. Open column cation-exchange radiochromatography 36 was carried out to show that more than 99% of the 51 Cr was initially present as Cr(VI).…”

Section: Reagentsmentioning

confidence: 99%

“…The elution was carried out using the following sequence of eluents: 12 mL of 0.01 mol L -1 HClO 4 for the elution of neutral and anionic species; 20 mL of 0.1 mol L -1 HClO 4 for the elution of +1 species; 20 mL of 1 mol L -1 HClO 4 for the elution of +2 species; 24 mL of 0.25 mol L -1 Ca(ClO 4 ) 2 at pH 2 (adjusted with HClO 4 ) for the elution of +3 species; 24 mL of 0.5 mol L -1 Ca(ClO 4 ) 2 at pH 2 and 24 mL of 1 mol L -1 Ca(ClO 4 ) 2 at pH 2 for the elution of dimeric, trimeric and polimeric species. 36 Two mL fractions of the eluates were collected (ISCO 328 fraction collector) for radioactivity measurements. The resin (R) was also counted to estimate possible non-eluting species.…”

Section: Speciation By Open Column Ion Exchange Chromatographymentioning

confidence: 99%

Reduction of trace quantities of chromium(VI) by strong acids

Pezzin¹,

Rivera²,

Collins³

2004

J. Braz. Chem. Soc.

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O comportamento químico de Cr(VI) a baixas concentrações (10-4 to 10-7 mol L-1) em vários ácidos fortes foi estudado utilizando-se 51 Cr(VI) de alta atividade específica como marcador. A especiação dos produtos destes sistemas foi realizada por cromatografia de troca iônica com eluição em etapas. Os resultados mostram que traços de Cr(VI), monitorados por radiocromo (51 Cr), são reduzidos na presença de ácidos minerais tais como perclórico, clorídrico, fluorídrico, sulfúrico, nítrico e trifluormetanosulfônico, mesmo na ausência de agentes redutores convencionais, produzindo várias espécies de Cr(III) diferentes, dependendo do ânion do ácido. Estudos detalhados com soluções de ácido nítrico mostram que a velocidade relativa da redução aumenta com o aumento da concentração do ácido ou com o decréscimo da concentração de Cr(VI). The chemical behavior of Cr(VI) at low concentrations (10-4 to 10-7 mol L-1) in several strong acids was studied using high specific activity 51 Cr(VI) as a tracer. The speciation of the products from these systems was carried out by ion exchange chromatography with stepwise elution. The results show that trace quantities of Cr(VI), monitored by means of radiochromium (51 Cr), are reduced in the presence of mineral acids such as perchloric, hydrochloric, hydrofluoric, sulfuric, nitric and trifluoromethanesulfonic acids, even in the absence of conventional reducing agents, producing different measureable Cr(III) species, depending on the acid anion. Detailed studies of the reduction of low concentrations of Cr(VI) with nitric acid have shown that the relative rate of reduction increases as the concentration of the acid increases or as the concentration of the Cr(VI) decreases.

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Column chromatographic speciation of chromium for Cr(VI) and several species of Cr(III)

Cited by 37 publications

References 18 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

A radiochromatograpic study of the reaction of ⁵¹CrO₃ with hydrochloric acid

Reduction of trace quantities of chromium(VI) by strong acids

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Column chromatographic speciation of chromium for Cr(VI) and several species of Cr(III)

Cited by 37 publications

References 18 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

A radiochromatograpic study of the reaction of 51CrO3 with hydrochloric acid

Reduction of trace quantities of chromium(VI) by strong acids

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A radiochromatograpic study of the reaction of ⁵¹CrO₃ with hydrochloric acid