Biological/biomedical accelerator mass spectrometry targets. 2. Physical, morphological, and structural characteristics.
The number of biological/biomedical applications that require AMS to achieve their goals is increasing, and so is the need for a better understanding of the physical, morphological, and structural traits of high quality of AMS targets. The metrics of quality included color, hardness/texture, and appearance (photo and SEM), along with FT-IR, Raman, and powder X-ray diffraction spectra that correlate positively with reliable and intense ion currents and accuracy, precision, and sensitivity of fraction modern ( F m). Our previous method produced AMS targets of gray-colored iron-carbon materials (ICM) 20% of the time and of graphite-coated iron (GCI) 80% of the time. The ICM was hard, its FT-IR spectra lacked the sp (2) bond, its Raman spectra had no detectable G' band at 2700 cm (-1), and it had more iron carbide (Fe 3C) crystal than nanocrystalline graphite or graphitizable carbon (g-C). ICM produced low and variable ion current whereas the opposite was true for the graphitic GCI. Our optimized method produced AMS targets of graphite-coated iron powder (GCIP) 100% of the time. The GCIP shared some of the same properties as GCI in that both were black in color, both produced robust ion current consistently, their FT-IR spectra had the sp (2) bond, their Raman spectra had matching D, G, G', D +G, and D '' bands, and their XRD spectra showed matching crystal size. GCIP was a powder that was easy to tamp into AMS target holders that also facilitated high throughput. We concluded that AMS targets of GCIP were a mix of graphitizable carbon and Fe 3C crystal, because none of their spectra, FT-IR, Raman, or XRD, matched exactly those of the graphite standard. Nevertheless, AMS targets of GCIP consistently produced the strong, reliable, and reproducible ion currents for high-throughput AMS analysis (270 targets per skilled analyst/day) along with accurate and precise F m values.
Kim
Seung-Hyun
SH
Department of Nutrition, University of California Davis, One Shields Avenue, Davis, California 95616, USA.
Kelly
Peter B
PB
Clifford
Andrew J
AJ
D003116:Color; D006108:Graphite / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D012680:Sensitivity and Specificity; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014961:X-Ray Diffraction
D006108:Graphite; D007501:Iron
Phys Chem Chem Phys. 2007 Mar 21;9(11):1276-91
17347700
Anal Chem. 2008 Oct 15;80(20):7651-60
18785761
Philos Trans A Math Phys Eng Sci. 2004 Nov 15;362(1824):2271-88
15482979
Angew Chem Int Ed Engl. 2001 Dec 3;40(23):4447-4449
12404441
Methods Enzymol. 2005;402:402-22
16401517
Am J Clin Nutr. 2004 Sep;80(3):680-91
15321809
Anal Chem. 2003 May 1;75(9):2192-6
12720362
Am J Clin Nutr. 2006 Dec;84(6):1430-41
17158427
Phys Rev B Condens Matter. 1990 Jun 15;41(17):12260-12263
9993681