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Quality of graphite target for biological/biomedical/environmental applications of 14C-accelerator mass spectrometry.

Kim SH, Kelly PB, Ortalan V, Browning ND, Clifford AJ - Anal. Chem. (2010)

Bottom Line: Catalytic graphitization for (14)C-accelerator mass spectrometry ((14)C-AMS) produced various forms of elemental carbon.Our high-throughput Zn reduction method (C/Fe = 1:5, 500 degrees C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe(3)C.Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental (14)C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition, University of California Davis, One Shields Avenue, Davis, California, 95616, USA.

ABSTRACT
Catalytic graphitization for (14)C-accelerator mass spectrometry ((14)C-AMS) produced various forms of elemental carbon. Our high-throughput Zn reduction method (C/Fe = 1:5, 500 degrees C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe(3)C. Crystallinity of the AMS targets of GCIP (nongraphitic carbon) was increased to turbostratic carbon by raising the C/Fe ratio from 1:5 to 1:1 and the graphitization temperature from 500 to 585 degrees C. The AMS target of GCIP containing turbostratic carbon had a large isotopic fractionation and a low AMS ion current. The AMS target of GCIP containing turbostratic carbon also yielded less accurate/precise (14)C-AMS measurements because of the lower graphitization yield and lower thermal conductivity that were caused by the higher C/Fe ratio of 1:1. On the other hand, the AMS target of GCIP containing nongraphitic carbon had higher graphitization yield and better thermal conductivity over the AMS target of GCIP containing turbostratic carbon due to optimal surface area provided by the iron powder. Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental (14)C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals.

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A model of graphite formation (a) and the carbon formations and transformations that may have occurred during graphitization using H2 or Zn dust as reductants (b). Initially, CO2 and/or CO were converted to iron carbides (especially, Fe3C) that saturated the surface of the iron particle. Then, graphite or graphite-like materials were produced on the iron carbide surface (a). The iron carbide may have acted as the catalyst for formation of graphite. The crystallinity of graphite and/or graphite-like materials increased as the C/Fe ratio increased and the CO2 reduction temperature increased, so that Ts carbon was produced directly with the C/Fe ratio of 1:1 at 585 °C for 3 h. Graphite material can be produced with the C/Fe ratio of 1:1 at >2500 °C. Furthermore, Ts can be produced from the nongraphitic carbon or Fe3C by HTT (broken red lines). Finally, graphite material was also produced by heat treatment temperature (HTT, > 2500 °C) alone from the nongraphitic, Ts carbon, or microcrystalline carbon (broken red lines).
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fig4: A model of graphite formation (a) and the carbon formations and transformations that may have occurred during graphitization using H2 or Zn dust as reductants (b). Initially, CO2 and/or CO were converted to iron carbides (especially, Fe3C) that saturated the surface of the iron particle. Then, graphite or graphite-like materials were produced on the iron carbide surface (a). The iron carbide may have acted as the catalyst for formation of graphite. The crystallinity of graphite and/or graphite-like materials increased as the C/Fe ratio increased and the CO2 reduction temperature increased, so that Ts carbon was produced directly with the C/Fe ratio of 1:1 at 585 °C for 3 h. Graphite material can be produced with the C/Fe ratio of 1:1 at >2500 °C. Furthermore, Ts can be produced from the nongraphitic carbon or Fe3C by HTT (broken red lines). Finally, graphite material was also produced by heat treatment temperature (HTT, > 2500 °C) alone from the nongraphitic, Ts carbon, or microcrystalline carbon (broken red lines).

Mentions: Our overall schematic of graphite formation and understanding of carbon structure formation/transformation with various C/Fe ratios, CO2 reduction temperatures, and/or heat treatment temperature (HTT, broken red lines) without catalyst activity were summarized in Figure 4. The CO2 and H2O from sample of interest were reduced to CO and H2 by oxidation of Zn dust. The CO2 and/or CO were the first formed iron carbides (especially, Fe3C). Then, the Fe particle saturated with Fe3C begins to reduce the graphite or graphite-like materials over the particle surface (Figure 4a).


Quality of graphite target for biological/biomedical/environmental applications of 14C-accelerator mass spectrometry.

Kim SH, Kelly PB, Ortalan V, Browning ND, Clifford AJ - Anal. Chem. (2010)

A model of graphite formation (a) and the carbon formations and transformations that may have occurred during graphitization using H2 or Zn dust as reductants (b). Initially, CO2 and/or CO were converted to iron carbides (especially, Fe3C) that saturated the surface of the iron particle. Then, graphite or graphite-like materials were produced on the iron carbide surface (a). The iron carbide may have acted as the catalyst for formation of graphite. The crystallinity of graphite and/or graphite-like materials increased as the C/Fe ratio increased and the CO2 reduction temperature increased, so that Ts carbon was produced directly with the C/Fe ratio of 1:1 at 585 °C for 3 h. Graphite material can be produced with the C/Fe ratio of 1:1 at >2500 °C. Furthermore, Ts can be produced from the nongraphitic carbon or Fe3C by HTT (broken red lines). Finally, graphite material was also produced by heat treatment temperature (HTT, > 2500 °C) alone from the nongraphitic, Ts carbon, or microcrystalline carbon (broken red lines).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2837469&req=5

fig4: A model of graphite formation (a) and the carbon formations and transformations that may have occurred during graphitization using H2 or Zn dust as reductants (b). Initially, CO2 and/or CO were converted to iron carbides (especially, Fe3C) that saturated the surface of the iron particle. Then, graphite or graphite-like materials were produced on the iron carbide surface (a). The iron carbide may have acted as the catalyst for formation of graphite. The crystallinity of graphite and/or graphite-like materials increased as the C/Fe ratio increased and the CO2 reduction temperature increased, so that Ts carbon was produced directly with the C/Fe ratio of 1:1 at 585 °C for 3 h. Graphite material can be produced with the C/Fe ratio of 1:1 at >2500 °C. Furthermore, Ts can be produced from the nongraphitic carbon or Fe3C by HTT (broken red lines). Finally, graphite material was also produced by heat treatment temperature (HTT, > 2500 °C) alone from the nongraphitic, Ts carbon, or microcrystalline carbon (broken red lines).
Mentions: Our overall schematic of graphite formation and understanding of carbon structure formation/transformation with various C/Fe ratios, CO2 reduction temperatures, and/or heat treatment temperature (HTT, broken red lines) without catalyst activity were summarized in Figure 4. The CO2 and H2O from sample of interest were reduced to CO and H2 by oxidation of Zn dust. The CO2 and/or CO were the first formed iron carbides (especially, Fe3C). Then, the Fe particle saturated with Fe3C begins to reduce the graphite or graphite-like materials over the particle surface (Figure 4a).

Bottom Line: Catalytic graphitization for (14)C-accelerator mass spectrometry ((14)C-AMS) produced various forms of elemental carbon.Our high-throughput Zn reduction method (C/Fe = 1:5, 500 degrees C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe(3)C.Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental (14)C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition, University of California Davis, One Shields Avenue, Davis, California, 95616, USA.

ABSTRACT
Catalytic graphitization for (14)C-accelerator mass spectrometry ((14)C-AMS) produced various forms of elemental carbon. Our high-throughput Zn reduction method (C/Fe = 1:5, 500 degrees C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe(3)C. Crystallinity of the AMS targets of GCIP (nongraphitic carbon) was increased to turbostratic carbon by raising the C/Fe ratio from 1:5 to 1:1 and the graphitization temperature from 500 to 585 degrees C. The AMS target of GCIP containing turbostratic carbon had a large isotopic fractionation and a low AMS ion current. The AMS target of GCIP containing turbostratic carbon also yielded less accurate/precise (14)C-AMS measurements because of the lower graphitization yield and lower thermal conductivity that were caused by the higher C/Fe ratio of 1:1. On the other hand, the AMS target of GCIP containing nongraphitic carbon had higher graphitization yield and better thermal conductivity over the AMS target of GCIP containing turbostratic carbon due to optimal surface area provided by the iron powder. Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental (14)C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals.

Show MeSH
Related in: MedlinePlus