title: Quality of graphite target for biological/biomedical/environmental applications of 14C-accelerator mass spectrometry.
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.
authors.affiliation: Department of Nutrition, University of California Davis, One Shields Avenue, Davis, California, 95616, USA.
authors.forename: Seung-Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Peter B
authors.initials: PB
authors.lastname: Kelly
authors.forename: Volkan
authors.initials: V
authors.lastname: Ortalan
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Browning
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Clifford
mesh_terms: D002250:Carbon Radioisotopes / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*
chemical_list: D002250:Carbon Radioisotopes; D006108:Graphite