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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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Comparisons of the isotopic fractionation (δ13C), graphitization yield, Fm (14C level), and ion currents (12C−, 13C+, n13C+) of the two AMS targets of GCIP with different graphite crystallinity. The AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had more ordered nanocrystalline graphite (Ts carbon, Lc ≈ 5 nm, d002 ≈ 0.335 nm in Figure 2) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) However, the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had an ≈0.7‰ larger isotopic fractionation (Figure 6a), a 9% lower graphitization yield (Figure 6b), a less accurate and precise Fm (relative error = 0.5743%, Figure 6c), and an ≈40% lower 12C−, 13C+, and n13C+ currents (Figure 6d−f) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) The n13C+ (Figure 6f) was unitless. The d002 in the GCIP (Ts carbon) as measured by XRD was ≈0.335 nm, while the d002 in the GCIP (Ts carbon) as measured by HRTEM (Figure 5e) was 0.342 nm.
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fig6: Comparisons of the isotopic fractionation (δ13C), graphitization yield, Fm (14C level), and ion currents (12C−, 13C+, n13C+) of the two AMS targets of GCIP with different graphite crystallinity. The AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had more ordered nanocrystalline graphite (Ts carbon, Lc ≈ 5 nm, d002 ≈ 0.335 nm in Figure 2) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) However, the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had an ≈0.7‰ larger isotopic fractionation (Figure 6a), a 9% lower graphitization yield (Figure 6b), a less accurate and precise Fm (relative error = 0.5743%, Figure 6c), and an ≈40% lower 12C−, 13C+, and n13C+ currents (Figure 6d−f) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) The n13C+ (Figure 6f) was unitless. The d002 in the GCIP (Ts carbon) as measured by XRD was ≈0.335 nm, while the d002 in the GCIP (Ts carbon) as measured by HRTEM (Figure 5e) was 0.342 nm.

Mentions: Figure 6 compared isotopic fractionation (δ13C), graphitization yield, and 14C-AMS measurements (ion currents, Fm) of two AMS targets of GCIP (as in Figure 5) with different graphite crystallinity. Although the AMS target of GCIP (Ts carbon, C/Fe ratio of 1:1, 585 °C, 3 h) had more ordered nanocrystalline graphite (Lc ≈ 5 nm in Figure 2), it showed an ≈0.7‰ lighter δ13C shift (Figure 6a) and 9% lower graphitization yield (Figure 6b) compared to those of the AMS target of GCIP (nongraphitic carbon8,11) (P < 0.0001). Although differences of Fm between the AMS targets of GCIP (Ts carbon) and GCIP (nongraphitic carbon) were not significant (P < 0.9804), the AMS target of GCIP (Ts carbon) had less accurate and precise Fm value (relative error of 0.57%) than the AMS target of GCIP (nongraphitic carbon,8,11 relative error of −0.02%) (Figure 6c). In addition, the AMS target of GCIP (Ts carbon) produced an ≈40% lower 12C−, 13C+, and normalized 13C+ (n13C+) currents (P < 0.0001) than the AMS target of GCIP (nongraphitic carbon8,11) (Figure 6d−f).


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)

Comparisons of the isotopic fractionation (δ13C), graphitization yield, Fm (14C level), and ion currents (12C−, 13C+, n13C+) of the two AMS targets of GCIP with different graphite crystallinity. The AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had more ordered nanocrystalline graphite (Ts carbon, Lc ≈ 5 nm, d002 ≈ 0.335 nm in Figure 2) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) However, the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had an ≈0.7‰ larger isotopic fractionation (Figure 6a), a 9% lower graphitization yield (Figure 6b), a less accurate and precise Fm (relative error = 0.5743%, Figure 6c), and an ≈40% lower 12C−, 13C+, and n13C+ currents (Figure 6d−f) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) The n13C+ (Figure 6f) was unitless. The d002 in the GCIP (Ts carbon) as measured by XRD was ≈0.335 nm, while the d002 in the GCIP (Ts carbon) as measured by HRTEM (Figure 5e) was 0.342 nm.
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fig6: Comparisons of the isotopic fractionation (δ13C), graphitization yield, Fm (14C level), and ion currents (12C−, 13C+, n13C+) of the two AMS targets of GCIP with different graphite crystallinity. The AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had more ordered nanocrystalline graphite (Ts carbon, Lc ≈ 5 nm, d002 ≈ 0.335 nm in Figure 2) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) However, the AMS target of GCIP (C/Fe = 1:1, 585 °C, 3 h) had an ≈0.7‰ larger isotopic fractionation (Figure 6a), a 9% lower graphitization yield (Figure 6b), a less accurate and precise Fm (relative error = 0.5743%, Figure 6c), and an ≈40% lower 12C−, 13C+, and n13C+ currents (Figure 6d−f) than the AMS target of GCIP (C/Fe = 1:5, 500 °C, 3 h).(11) The n13C+ (Figure 6f) was unitless. The d002 in the GCIP (Ts carbon) as measured by XRD was ≈0.335 nm, while the d002 in the GCIP (Ts carbon) as measured by HRTEM (Figure 5e) was 0.342 nm.
Mentions: Figure 6 compared isotopic fractionation (δ13C), graphitization yield, and 14C-AMS measurements (ion currents, Fm) of two AMS targets of GCIP (as in Figure 5) with different graphite crystallinity. Although the AMS target of GCIP (Ts carbon, C/Fe ratio of 1:1, 585 °C, 3 h) had more ordered nanocrystalline graphite (Lc ≈ 5 nm in Figure 2), it showed an ≈0.7‰ lighter δ13C shift (Figure 6a) and 9% lower graphitization yield (Figure 6b) compared to those of the AMS target of GCIP (nongraphitic carbon8,11) (P < 0.0001). Although differences of Fm between the AMS targets of GCIP (Ts carbon) and GCIP (nongraphitic carbon) were not significant (P < 0.9804), the AMS target of GCIP (Ts carbon) had less accurate and precise Fm value (relative error of 0.57%) than the AMS target of GCIP (nongraphitic carbon,8,11 relative error of −0.02%) (Figure 6c). In addition, the AMS target of GCIP (Ts carbon) produced an ≈40% lower 12C−, 13C+, and normalized 13C+ (n13C+) currents (P < 0.0001) than the AMS target of GCIP (nongraphitic carbon8,11) (Figure 6d−f).

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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