Limits...
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.

Show MeSH

Related in: MedlinePlus

Comparison of HRTEM measurements of the AMS target of GCIP(11) and the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h). Both AMS targets of GCIP consisted of carbon (/or graphite) sheet (a and e) and the carbon-encapsulated Fe (C-Fe, b and f). Enlarged images of the carbon sheet (a and e) and the C-Fe (b and f) matched the red rectangle area in each insert TEM image. The carbon sheet in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was more ordered (d002 = 0.342 nm) and thicker (6.7 nm) than that of the AMS target of GCIP(11) (a and e). The carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was thicker (10.7 nm) than that in the AMS target of GCIP(11) (4.9 nm). However, the carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was a less ordered carbon (b and f) compared to that in the AMS target of GCIP(11). Although all graphitization processes were conducted under identical conditions, carbon shell thickness in the AMS target of GCIP was variable, because our Fe particle size was not uniform. STEM-EELS showed ordered, semiordered, and amorphous carbons in both AMS targets of GCIP. The EELS of both AMS targets of GCIP were consistent for those of graphite and a-C in a prior study(28) (c and g). The STEM-EELS line scan was performed to check the Fe composition along the C-Fe interface, along the green line (d and h). The distance between each spectrum was about 0.3 nm, and it was normalized to the FeL3 intensity along the green line. Even though the Fe3C in the C-Fe was not uniform, it was detected by ≈5 nm deep into the Fe particle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2837469&req=5

fig5: Comparison of HRTEM measurements of the AMS target of GCIP(11) and the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h). Both AMS targets of GCIP consisted of carbon (/or graphite) sheet (a and e) and the carbon-encapsulated Fe (C-Fe, b and f). Enlarged images of the carbon sheet (a and e) and the C-Fe (b and f) matched the red rectangle area in each insert TEM image. The carbon sheet in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was more ordered (d002 = 0.342 nm) and thicker (6.7 nm) than that of the AMS target of GCIP(11) (a and e). The carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was thicker (10.7 nm) than that in the AMS target of GCIP(11) (4.9 nm). However, the carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was a less ordered carbon (b and f) compared to that in the AMS target of GCIP(11). Although all graphitization processes were conducted under identical conditions, carbon shell thickness in the AMS target of GCIP was variable, because our Fe particle size was not uniform. STEM-EELS showed ordered, semiordered, and amorphous carbons in both AMS targets of GCIP. The EELS of both AMS targets of GCIP were consistent for those of graphite and a-C in a prior study(28) (c and g). The STEM-EELS line scan was performed to check the Fe composition along the C-Fe interface, along the green line (d and h). The distance between each spectrum was about 0.3 nm, and it was normalized to the FeL3 intensity along the green line. Even though the Fe3C in the C-Fe was not uniform, it was detected by ≈5 nm deep into the Fe particle.

Mentions: HRTEM was used to characterize and confirm morphology and crystalline structure of two GCIPs. One was produced with our HT Zn reduction method.(11) The other was produced with the same method,(11) except for using C/Fe ratio of 1:1 at 585 °C (Figure 5).


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)

Comparison of HRTEM measurements of the AMS target of GCIP(11) and the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h). Both AMS targets of GCIP consisted of carbon (/or graphite) sheet (a and e) and the carbon-encapsulated Fe (C-Fe, b and f). Enlarged images of the carbon sheet (a and e) and the C-Fe (b and f) matched the red rectangle area in each insert TEM image. The carbon sheet in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was more ordered (d002 = 0.342 nm) and thicker (6.7 nm) than that of the AMS target of GCIP(11) (a and e). The carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was thicker (10.7 nm) than that in the AMS target of GCIP(11) (4.9 nm). However, the carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was a less ordered carbon (b and f) compared to that in the AMS target of GCIP(11). Although all graphitization processes were conducted under identical conditions, carbon shell thickness in the AMS target of GCIP was variable, because our Fe particle size was not uniform. STEM-EELS showed ordered, semiordered, and amorphous carbons in both AMS targets of GCIP. The EELS of both AMS targets of GCIP were consistent for those of graphite and a-C in a prior study(28) (c and g). The STEM-EELS line scan was performed to check the Fe composition along the C-Fe interface, along the green line (d and h). The distance between each spectrum was about 0.3 nm, and it was normalized to the FeL3 intensity along the green line. Even though the Fe3C in the C-Fe was not uniform, it was detected by ≈5 nm deep into the Fe particle.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig5: Comparison of HRTEM measurements of the AMS target of GCIP(11) and the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h). Both AMS targets of GCIP consisted of carbon (/or graphite) sheet (a and e) and the carbon-encapsulated Fe (C-Fe, b and f). Enlarged images of the carbon sheet (a and e) and the C-Fe (b and f) matched the red rectangle area in each insert TEM image. The carbon sheet in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was more ordered (d002 = 0.342 nm) and thicker (6.7 nm) than that of the AMS target of GCIP(11) (a and e). The carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was thicker (10.7 nm) than that in the AMS target of GCIP(11) (4.9 nm). However, the carbon shell in the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) was a less ordered carbon (b and f) compared to that in the AMS target of GCIP(11). Although all graphitization processes were conducted under identical conditions, carbon shell thickness in the AMS target of GCIP was variable, because our Fe particle size was not uniform. STEM-EELS showed ordered, semiordered, and amorphous carbons in both AMS targets of GCIP. The EELS of both AMS targets of GCIP were consistent for those of graphite and a-C in a prior study(28) (c and g). The STEM-EELS line scan was performed to check the Fe composition along the C-Fe interface, along the green line (d and h). The distance between each spectrum was about 0.3 nm, and it was normalized to the FeL3 intensity along the green line. Even though the Fe3C in the C-Fe was not uniform, it was detected by ≈5 nm deep into the Fe particle.
Mentions: HRTEM was used to characterize and confirm morphology and crystalline structure of two GCIPs. One was produced with our HT Zn reduction method.(11) The other was produced with the same method,(11) except for using C/Fe ratio of 1:1 at 585 °C (Figure 5).

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