Chemical separation and MC-ICPMS analysis of U, Th, Pa and Ra isotope ratios of carbonates

2018 ◽  
Vol 33 (8) ◽  
pp. 1372-1383 ◽  
Author(s):  
J. Christina Obert ◽  
Denis Scholz ◽  
Jörg Lippold ◽  
Thomas Felis ◽  
Klaus Peter Jochum ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Chemical Separation ◽  
Isotope Ratios ◽  
Carbonate Sample

Ion exchange chemistry and MC-ICPMS measurements of U, Th, Pa and Ra isotope ratios from the same carbonate sample.

scholarly journals Stable Isotopes of Platinum: Measurement and Application to Constraining the Formation and Differentiation of Earth

2021 ◽  
Author(s):  
◽  
John Creech
Keyword(s):  
Stable Isotope ◽  
Inductively Coupled Plasma ◽  
Chemical Separation ◽  
Isotope Ratios ◽  
Stable Isotope Ratios ◽  
Core Formation ◽  
Inductively Coupled ◽  
Earth’S Mantle ◽  
Isotope System ◽  
Late Veneer

<p>A wide range of novel, non-traditional, stable isotope systems have been developed over the last decade, largely as a result of the advent of multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS), and continue to provide valuable new insights in the earth, environmental and planetary sciences. The platinum (Pt) stable isotope system represents a potentially powerful but, as yet, unexplored addition to this suite of stable isotope tracers. Pt has six naturally occurring isotopes, and can exist in a range of oxidation states. The geochemical behaviour of Pt coupled with the relatively large mass difference (ca. 2%) between the abundant heavy and light isotopes and its variable oxidation states leads to potential applications in tracing a range of natural processes. In particular, the strong elemental partitioning of Pt between metals and silicates makes the Pt stable isotope system uniquely suited to tracing processes of Earth’s accretion and differentiation. This study aims to develop new techniques for measurement of Pt stable isotopes in geological samples, and to apply these to terrestrial and meteorite samples to attempt to resolve outstanding questions relating to Earth’s early evolution.  A technique was developed for measurement of Pt stable isotope ratios using multiple collector inductively coupled plasma mass spectrometry (MCICPMS), employing a ¹⁹⁶Pt–¹⁹⁸Pt double-spike to correct for instrumental mass fractionation. Results are reported in terms of δ¹⁹⁸Pt, which represents the per mil difference in the ¹⁹⁸Pt/¹⁹⁴Pt ratio from the IRMM-010 Pt isotope standard. A range of analytical tests were conducted and show that this approach has a reproducibility of ca. ±0.04 %∘ on δ¹⁹⁸Pt (i.e., ±0.01%∘ amu⁻¹) for Pt solution standards, and is insensitive to minor amounts of matrix that may be retained after chemical purification of Pt. Measurements of Pt solution standards conducted using two different MC-ICPMS instruments showed resolvable variations, which suggest that natural fractionations exist that exceed the reproducibility of the technique.  Techniques were also developed for dissolution of natural samples and chemical separation of Pt. Geological standards were digested using a nickel sulphide fire assay technique, which pre-concentrates the highly siderophile elements in a NiS bead that is readily dissolved in acid. This was followed by chemical separation of Pt from digested samples using anion exchange chemical techniques. Elution curves were constructed for a range of synthetic rock matrices. These tests show that Pt separation is achieved with >90% Pt yield and ca. 95% purity. Analytical tests show that this level of Pt separation is sufficient for accurate determination of Pt stable isotope ratios by double-spike MC-ICPMS. These techniques were then applied to 11 international geological standard reference materials representing mantle peridotites, igneous samples, and Pt ore materials. The reproducibility in natural samples was determined by processing multiple replicate digestions of a standard reference material, and was shown to be ca. ±0.08%∘ (2 sd). Pt stable isotope data for the full set of reference materials have a range of δ¹⁹⁸Pt values with offsets of up to 0.40%∘ from the IRMM-010 standard, which are readily resolved with this technique. Mantle samples yielded the lightest (most negative) isotopic compositions of the terrestrial standards, with igneous and Pt ore samples defining a continuous trend towards zero, which is consistent with the IRMM-010 standard being derived from a Pt ore. These results demonstrate the potential of the Pt isotope system as a tracer in geochemical systems.  The techniques developed above were then applied to investigate an outstanding problem relating to Earth’s accretion and differentiation. Highly siderophile elements (HSE) are strongly partitioned into the cores of terrestrial planets during core formation, and the abundances of HSE in Earth’s mantle compared with primitive meteorites have provided key constraints on models of Earth’s early evolution. Two leading models to explain the HSE abundances in the silicate Earth involve either a late-veneer of chondritic material that was added after core formation or core formation in a deep magma ocean. The platinum (Pt) stable isotope system represents a novel tool for investigating these processes. Using the techniques developed above, Pt stable isotope ratios were measured in a range of meteorite samples, including enstatite, ordinary and carbonaceous chondrites, primitive achondrites, achondrites and iron meteorites, as well as additional terrestrial mantle xenolith samples. Our data set reveals that the Pt stable isotopic composition of Earth’s mantle overlaps with all of the chondrite groups. Primitive achondrite and ureilite samples revealed the heaviest compositions of all meteorite groups. These data suggest that metal–silicate differentiation produces an isotopic fractionation for Pt, with heavy isotopes being preferentially retained in the silicate phase. Thus, Earth’s mantle is expected to have been significantly enriched in the heavy isotopes of Pt during core formation, even if metal–silicate differentiation took place in a magma ocean. The absence of a large fractionation between chondrites, representing the composition of the undifferentiated Earth, and the mantle suggests that the signature of core formation in the mantle has been subsequently overprinted. Considering the overlap between the Pt stable isotopic compositions of the mantle and chondrites, the most likely means for overprinting the composition of the mantle is by addition of a chondritic late-veneer. Mixing calculations show that addition of 0.5% of Earth’s mass by a late-veneer of chondritic material would be sufficient to overprint highly fractionated Pt stable isotope signatures resulting from core-formation.</p>

THE USE OF ISOTOPE DILUTION IN DETERMINATION OF GEOLOGIC AGE OF MINERALS

1953 ◽  
Vol 31 (10) ◽  
pp. 909-914 ◽  
Author(s):  
R. H. Tomlinson ◽  
A. K. Das Gupta
Keyword(s):  
Ion Exchange ◽  
Mass Spectrometer ◽  
Isotope Dilution ◽  
Chemical Separation ◽  
Mass Spectrometric ◽  
Dilution Technique ◽  
Isotope Dilution Technique ◽  
Mass Spectrometric Determination

The mass spectrometer has been used for the estimation of trace quantities of rubidium and strontium. The isotope dilution technique developed by Aldrich has been extended so that 0.01% of rubidium and 0.0001% strontium have been analyzed with 100 mgm. of mineral. The use of small quantities for mass spectrometric determination allows the use of easily available fission strontium and rubidium. The radioactivity of the fission strontium also simplifies the chemical manipulation. No chemical separation from the mineral was required for the rubidium but the strontium was concentrated by ion exchange methods. Ages are presented for one lepidolite and two biotite minerals and their ages compared to those found by other methods. With one of the biotites the effect of weathering on the fractionation of rubidium from strontium has been studied.

scholarly journals Stable Isotopes of Platinum: Measurement and Application to Constraining the Formation and Differentiation of Earth

2021 ◽  
Author(s):  
◽  
John Creech
Keyword(s):  
Stable Isotope ◽  
Inductively Coupled Plasma ◽  
Chemical Separation ◽  
Isotope Ratios ◽  
Stable Isotope Ratios ◽  
Core Formation ◽  
Inductively Coupled ◽  
Earth’S Mantle ◽  
Isotope System ◽  
Late Veneer

<p>A wide range of novel, non-traditional, stable isotope systems have been developed over the last decade, largely as a result of the advent of multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS), and continue to provide valuable new insights in the earth, environmental and planetary sciences. The platinum (Pt) stable isotope system represents a potentially powerful but, as yet, unexplored addition to this suite of stable isotope tracers. Pt has six naturally occurring isotopes, and can exist in a range of oxidation states. The geochemical behaviour of Pt coupled with the relatively large mass difference (ca. 2%) between the abundant heavy and light isotopes and its variable oxidation states leads to potential applications in tracing a range of natural processes. In particular, the strong elemental partitioning of Pt between metals and silicates makes the Pt stable isotope system uniquely suited to tracing processes of Earth’s accretion and differentiation. This study aims to develop new techniques for measurement of Pt stable isotopes in geological samples, and to apply these to terrestrial and meteorite samples to attempt to resolve outstanding questions relating to Earth’s early evolution.  A technique was developed for measurement of Pt stable isotope ratios using multiple collector inductively coupled plasma mass spectrometry (MCICPMS), employing a ¹⁹⁶Pt–¹⁹⁸Pt double-spike to correct for instrumental mass fractionation. Results are reported in terms of δ¹⁹⁸Pt, which represents the per mil difference in the ¹⁹⁸Pt/¹⁹⁴Pt ratio from the IRMM-010 Pt isotope standard. A range of analytical tests were conducted and show that this approach has a reproducibility of ca. ±0.04 %∘ on δ¹⁹⁸Pt (i.e., ±0.01%∘ amu⁻¹) for Pt solution standards, and is insensitive to minor amounts of matrix that may be retained after chemical purification of Pt. Measurements of Pt solution standards conducted using two different MC-ICPMS instruments showed resolvable variations, which suggest that natural fractionations exist that exceed the reproducibility of the technique.  Techniques were also developed for dissolution of natural samples and chemical separation of Pt. Geological standards were digested using a nickel sulphide fire assay technique, which pre-concentrates the highly siderophile elements in a NiS bead that is readily dissolved in acid. This was followed by chemical separation of Pt from digested samples using anion exchange chemical techniques. Elution curves were constructed for a range of synthetic rock matrices. These tests show that Pt separation is achieved with >90% Pt yield and ca. 95% purity. Analytical tests show that this level of Pt separation is sufficient for accurate determination of Pt stable isotope ratios by double-spike MC-ICPMS. These techniques were then applied to 11 international geological standard reference materials representing mantle peridotites, igneous samples, and Pt ore materials. The reproducibility in natural samples was determined by processing multiple replicate digestions of a standard reference material, and was shown to be ca. ±0.08%∘ (2 sd). Pt stable isotope data for the full set of reference materials have a range of δ¹⁹⁸Pt values with offsets of up to 0.40%∘ from the IRMM-010 standard, which are readily resolved with this technique. Mantle samples yielded the lightest (most negative) isotopic compositions of the terrestrial standards, with igneous and Pt ore samples defining a continuous trend towards zero, which is consistent with the IRMM-010 standard being derived from a Pt ore. These results demonstrate the potential of the Pt isotope system as a tracer in geochemical systems.  The techniques developed above were then applied to investigate an outstanding problem relating to Earth’s accretion and differentiation. Highly siderophile elements (HSE) are strongly partitioned into the cores of terrestrial planets during core formation, and the abundances of HSE in Earth’s mantle compared with primitive meteorites have provided key constraints on models of Earth’s early evolution. Two leading models to explain the HSE abundances in the silicate Earth involve either a late-veneer of chondritic material that was added after core formation or core formation in a deep magma ocean. The platinum (Pt) stable isotope system represents a novel tool for investigating these processes. Using the techniques developed above, Pt stable isotope ratios were measured in a range of meteorite samples, including enstatite, ordinary and carbonaceous chondrites, primitive achondrites, achondrites and iron meteorites, as well as additional terrestrial mantle xenolith samples. Our data set reveals that the Pt stable isotopic composition of Earth’s mantle overlaps with all of the chondrite groups. Primitive achondrite and ureilite samples revealed the heaviest compositions of all meteorite groups. These data suggest that metal–silicate differentiation produces an isotopic fractionation for Pt, with heavy isotopes being preferentially retained in the silicate phase. Thus, Earth’s mantle is expected to have been significantly enriched in the heavy isotopes of Pt during core formation, even if metal–silicate differentiation took place in a magma ocean. The absence of a large fractionation between chondrites, representing the composition of the undifferentiated Earth, and the mantle suggests that the signature of core formation in the mantle has been subsequently overprinted. Considering the overlap between the Pt stable isotopic compositions of the mantle and chondrites, the most likely means for overprinting the composition of the mantle is by addition of a chondritic late-veneer. Mixing calculations show that addition of 0.5% of Earth’s mass by a late-veneer of chondritic material would be sufficient to overprint highly fractionated Pt stable isotope signatures resulting from core-formation.</p>

scholarly journals A rapid and efficient ion-exchange chromatography for Lu–Hf, Sm–Nd, and Rb–Sr geochronology and the routine isotope analysis of sub-ng amounts of Hf by MC-ICP-MS

2015 ◽  
Vol 30 (11) ◽  
pp. 2323-2333 ◽  
Author(s):  
R. Bast ◽  
E. E. Scherer ◽  
P. Sprung ◽  
M. Fischer-Gödde ◽  
A. Stracke ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Isotope Analysis ◽  
Chemical Separation ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Separation Technique ◽  
Small Samples ◽  
Icp Ms

We present an effective chemical separation technique for Lu–Hf geochronology on small samples (sub-ng range Hf) and precise 176Hf/177Hf analysis.

scholarly journals Chemical Separation of Uranium and Precise Measurement of 234U/238U and 235U/238U Ratios in Soil Samples Using Multi Collector Inductively Coupled Plasma Mass Spectrometry

Molecules ◽  
2020 ◽  
Vol 25 (9) ◽  
pp. 2138 ◽  
Author(s):  
Nimelan Veerasamy ◽  
Asako Takamasa ◽  
Rajamanickam Murugan ◽  
Sharayu Kasar ◽  
Tatsuo Aono ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Chemical Separation ◽  
Isotope Ratios ◽  
Soil Samples ◽  
Spectrometric Method ◽  
Mass Spectrometric Method ◽  
Ratio Measurement ◽  
High Background ◽  
Inductively Coupled ◽  
Relative Standard

A new chemical separation has been developed to isolate uranium (U) using two UTEVA columns to minimize iron and thorium interferences from high background area soil samples containing minerals like monazites and ilmenite. The separation method was successfully verified in some certified reference materials (CRMs), for example, JSd-2, JLk-1, JB-1 and JB-3. The same method was applied for purification of U in Fukushima soil samples affected by the Fukushima dai-ichi nuclear power station (FDNPS) accident. Precise and accurate measurement of 234U/238U and 235U/238U isotope ratios in chemically separated U were carried out using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). In this mass spectrometric method, an array of two Faraday cups (1011 Ω, 1012 Ω resistor) and a Daly detector were simultaneously employed. The precision of U isotope ratios in an in-house standard was evaluated by replicate measurement. Relative standard deviation (RSD) of 234U/238U and 235U/238U were found to be 0.094% (2σ) and 0.590% (2σ), respectively. This method has been validated using a standard reference material SRM 4350B, sediment sample. The replicate measurements of 234U/238U in SRM shows 0.7% (RSD). This developed method is suitable for separation of U and its isotope ratio measurement in environmental samples.

scholarly journals Analytical Methods for Os Isotope Ratios and Re-PGE Mass Fractions in Geological Samples

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhuyin Chu
Keyword(s):  
Analytical Methods ◽  
Chemical Separation ◽  
Isotope Ratios ◽  
Measurement Methods ◽  
Data Quality Control ◽  
Geological Materials ◽  
Sample Dissolution ◽  
Mass Fractions ◽  
Comprehensive Reference

The recent advances in analytical methods of Re-Os and PGE in geological materials including sample dissolution, chemical separation, mass spectrometric determinations, as well as the developments of matrix-matched reference materials for data quality control are thoroughly reviewed. Further, the in-situ measurement methods for Re-PGE mass fractions and 187Os/188Os ratios, as well as the measurement methods for stable isotope ratios of Re and PGE are also briefly reviewed. This review stands as a comprehensive reference for researchers to consider in the development of measurement methods for Re-PGE mass fractions and 187Os/188Os ratios in geological materials.

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