Department of Nutrition, University of California Davis, One Shields Avenue, Davis, California, 95616, USA.
Anal Chem. 2010 Mar 15;82(6):2243-52. doi: 10.1021/ac9020769.
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.
用于（14）C-加速质谱（（14）C-AMS）的催化石墨化产生了各种形式的元素碳。我们的高通量 Zn 还原方法（C/Fe = 1:5、500°C、3 h）产生了石墨包覆铁粉（GCIP）的 AMS 靶，这是一种无定形碳和 Fe(3)C 的混合物。通过将 C/Fe 比从 1:5 提高到 1:1 和将石墨化温度从 500°C 提高到 585°C，GCIP（无定形碳）的 AMS 靶的结晶度增加到乱层石墨碳。GCIP 含有乱层石墨碳的 AMS 靶具有较大的同位素分馏和较低的 AMS 离子电流。GCIP 含有乱层石墨碳的 AMS 靶也由于较高的 C/Fe 比为 1:1 而导致较低的石墨化产率和较低的热导率，从而导致更不准确/不准确的（14）C-AMS 测量。另一方面，由于铁粉提供的最佳表面积，GCIP 含有无定形碳的 AMS 靶的石墨化产率和热导率均高于 GCIP 含有乱层石墨碳的 AMS 靶。最后，石墨化产率和热导率是准确/准确/高通量生物、生物医学和环境（14）C-AMS 应用的更重要决定因素（超过石墨结晶度），例如吸收、分布、代谢、消除（ADME）和基于生理学的药代动力学（PBPK）营养物质、药物、植物化学物质和环境化学物质。
