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Iron-Manganese System for Preparation of Radiocarbon Ams Targets: Characterization of Procedural Chemical-Isotopic Blanks and Fractionation

Published online by Cambridge University Press:  18 July 2016

R. Michael Verkouteren
Affiliation:
Surface and Microanalysis Science Division, National Institute of Standards and Technology Gaithersburg, Maryland 20899 USA
Donna B. Klinedinst
Affiliation:
Surface and Microanalysis Science Division, National Institute of Standards and Technology Gaithersburg, Maryland 20899 USA
Lloyd A. Currie
Affiliation:
Surface and Microanalysis Science Division, National Institute of Standards and Technology Gaithersburg, Maryland 20899 USA
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Abstract

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We report a practical system to mass-produce accelerator mass spectrometry (AMS) targets with 10–100 μg carbon samples. Carbon dioxide is reduced quantitatively to graphite on iron fibers via manganese metal, and the Fe-C fibers are melted into a bead suitable for AMS. Pretreatment, reduction and melting processes occur in sealed quartz tubes, allowing parallel processing for otherwise time-intensive procedures.

Chemical and isotopic (13C, 14C) blanks, target yields and isotopic fractionation were investigated with respect to levels of sample size, amounts of Fe and Mn, pretreatment and reduction time, and hydrogen pressure. With 7-day pretreatments, carbon blanks exhibited a lognormal mass distribution of 1.44 μg (central mean) with a dispersion of 0.50 μg (standard deviation). Reductions of 10 μg carbon onto targets were complete in 3–6 h with all targets, after correction for the blank, reflecting the 13C signature of the starting material. The 100 μg carbon samples required at least 15 h for reduction; shorter durations resulted in isotopic fractionation as a function of chemical yield. The trend in the 13C data suggested the presence of kinetic isotope effects during the reduction. The observed CO2-graphite 13C fractionation factor was 3–4% smaller than the equilibrium value in the simple Rayleigh model. The presence of hydrogen promoted methane formation in yields up to 25%.

Fe-C beaded targets were made from NIST Standard Reference Materials and compared with graphitic standards. Although the 12C ion currents from the beads were one to two orders of magnitude lower than currents from the graphite, measurements of the beaded standards were reproducible and internally consistent. Measurement reproducibility was limited mainly by Poisson counting statistics and blank variability, translating to 14C uncertainties of 5–1% for 10–100 μg carbon samples, respectively. A bias of 5–7% (relative) was observed between the beaded and graphitic targets, possibly due to variations in sputtering fractionation dependent on sample size, chemical form and beam geometry.

Type
Research Article
Copyright
Copyright © The American Journal of Science 

References

Aerts-Bijma, A. Th., Meijer, H. A. J. and van der Plicht, J. 1997 AMS sample handling in Groningen. In Jull, A. J. T., Beck, J. W. and Burr, G. S., eds., Proceedings of the 7th International Conference on Accelerator Mass Spectrometry (AMS-7). Nuclear Instruments and Methods in Physics Research B123: 221225.Google Scholar
Allison, C. E., Francey, R. J. and Meijer, H. A. J. 1995 Recommendations for the reporting of stable isotope measurements of carbon and oxygen in CO2 gas. In Reference and Intercomparison Materials for Stable Isotopes of Light Elements . IAEA–TECDOC–825. Vienna, International Atomic Energy Agency: 155162.Google Scholar
Barin, I. 1993 Thermochemical Data of Pure Substances, Parts I–II . 2nd ed. New York, VCH.Google Scholar
Bottinga, Y. 1969a Carbon isotope fractionation between graphite, diamond and carbon dioxide. Earth and Planetary Science Letters 5: 301307.Google Scholar
Bottinga, Y. 1969b Calculated fractionation factors for carbon and hydrogen isotope exchange in the system calcite-CO2-graphite-methane-hydrogen and water vapor. Geochimica et Cosmochimica Acta 33: 4964.CrossRefGoogle Scholar
Box, G. E. P., Hunter, W. G. and Hunter, J. S. 1978 Statistics for Experimenters . New York: John Wiley & Sons: 653 p.Google Scholar
Currie, L. A. 1994 Optimal estimation of uncertainty intervals for accelerator and decay counting. Nuclear Instruments and Methods in Physics Research B92: 188193.Google Scholar
Currie, L. A. (ms.) 1995 Fundamental limits to dating and isotope ratio uncertainties due to the multivariate isotopic-chemical blank. Paper presented at the 209th American Chemical Society National Meeting, NUCL034, Anaheim, California, 2–6 April.Google Scholar
Deer, W. A., Howie, R. A. and Zussman, J. 1962 Rock-Forming Minerals. Vol. 5. Non-Silicates . London, Longmans: 267 p.Google Scholar
Desai, P. D. 1987 Thermodynamic properties of manganese and molybdenum. Journal of Physical and Chemical Reference Data 16(1): 91108.Google Scholar
Donahue, D. J., Beck, J. W., Biddulph, D., Burr, G. S., Courtney, C., Damon, P. E., Hatheway, A. L., Hewitt, L., Jull, A. J. T., Lange, T., Lifton, N., Maddock, R., McHargue, L. R., O'Malley, J. M. and Toolin, L. J. 1997 Status of the NSF-Arizona AMS laboratory. Nuclear Instruments and Methods in Physics Research B123: 5156.Google Scholar
Engel, M. H. and Maynard, R. J. 1989 Preparation of organic matter for stable carbon isotope analysis by sealed tube combustion: A cautionary note. Analytical Chemistry 61, 19961998.Google Scholar
Fritz, P. and Fontes, J.-Ch. 1980 Introduction. In Fritz, P. and Fontes, J.-Ch. eds., Handbook of Environmental Isotope Geochemistry. Volume 1. The Terrestrial Environment , Amsterdam, Elsevier: 119.Google Scholar
Gonfiantini, R. 1981 The δ–notation and the mass-spectrometric techniques. In Stable Isotope Hydrology: Deuterium and Oxygen–18 in the Water Cycle . IAEA–TECDOC–210. Vienna, International Atomic Energy Agency: 14441448.Google Scholar
Hammersley, J. M. and Handscomb, D. C. 1964 Monte Carlo Methods . New York, John Wiley & Sons: 178 p.Google Scholar
Hut, G. 1987 Consultants' Group Meeting on Stable Isotope Reference Samples for Geochemical and Hydro-logical Investigations . Vienna, International Atomic Energy Agency: 42p.Google Scholar
ISO 1993 Guide to the Expression of Uncertainty in Measurement . Geneva, International Organization for Standardization: 101p.Google Scholar
Jehn, H., Speck, H., Fromm, E. and Hörz, G. 1981 Gases and Carbon in Metals (Thermodynamics, Kinetics, and Properties). Part 12. Group VIIA Metals . Physics Data No. 5–12.Google Scholar
Jull, A. J. T., Donahue, D. J., Hatheway, A. L., Linick, T. W. and Toolin, L. J. 1986 Production of graphite targets by deposition from CO/H2 for precision accelerator 14C measurements. In Stuiver, M. and Kra, R., eds., Proceedings of the 12th International 14C Conference. Radiocarbon 28(2A): 191197.Google Scholar
Kirner, D. L., Taylor, R. E. and Southon, J. R. 1995 Reduction in backgrounds of microsamples for AMS 14C dating. In Cook, G. T., Harkness, D. D., Miller, B. F. and Scott, E. M., eds., Proceedings of the 15th International 14C Conference. Radiocarbon 37(2): 697704.Google Scholar
Kitagawa, H., Masuzawa, T., Makamura, T. and Matsumoto, E. 1993 A batch preparation method for graphite targets with low background for AMS 14C measurements. Radiocarbon 35(2): 295300.Google Scholar
Klinedinst, D. B., McNichol, A. P., Currie, L. A., Schneider, R. J., Klouda, G. A., von Reden, K. F., Verkouteren, R. M. and Jones, G. A. 1994 Comparative study of Fe–C bead and graphite target performance with the National Ocean Science AMS (NOSAMS) facility recombinator ion source. Nuclear Instruments and Methods in Physics Research B92: 166171.Google Scholar
Mann, W. B. 1983 An international reference material for radiocarbon dating. In Stuiver, M. and Kra, R. S., eds., Proceedings of the 11th International 14C Conference. Radiocarbon 25(2): 519527.CrossRefGoogle Scholar
McNichol, A. P., Gagnon, A. R., Jones, G. A. and Osborne, E. A. 1992 Illumination of a black box: Analysis of gas composition during graphite target preparation. In Long, A. and Kra, R. S., eds., Proceedings of the 14th International 14C Conference. Radiocarbon 34(3): 321329.Google Scholar
McNichol, A. P., Gagnon, A. R., Osborne, E. A., Hutton, D. L., von Reden, K. F. and Schneider, R. J. 1995 Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation. In Cook, G. T., Harkness, D. D., Miller, B. F. and Scott, E. M., eds., Proceedings of the 15th International 14C Conference. Radiocarbon 37(2): 683692.Google Scholar
Mook, W. G. 1984 Archaeological and geological interest in applying 14C AMS to small samples. In Wölfli, W., Polach, H. A. and Anderson, H. H., eds., Proceedings of the 3rd International Symposium on Accelerator Mass Spectrometry. Nuclear Instruments and Methods in Physics Research 233(B5): 297302.CrossRefGoogle Scholar
Nadeau, M.-J., Kieser, W. E., Beukens, R. P. and Litherland, A. E. 1987 Quantum mechanical effects on sputter source isotope fractionation. In Gove, H. E., Litherland, A. E. and Elmore, D., eds., Proceedings of the 4rd International Symposium on Accelerator Mass Spectrometry. Nuclear Instruments and Methods in Physics Research B29: 8386.CrossRefGoogle Scholar
Olsson, R. G. and Turkdogan, E. T. 1974 Catalytic effect of iron on decomposition of carbon monoxide: II. Effect of additions of H2, H2O, CO2, SO2 and H2S. Metallurgical Transactions 5: 2126.Google Scholar
Polach, H. A. 1984 Radiocarbon targets for AMS: A review of perceptions, aims and achievements. In Wölfli, W., Polach, H. A. and Anderson, H. H., eds., Proceedings of the 3rd International Symposium on Accelerator Mass Spectrometry. Nuclear Instruments and Methods in Physics Research 233(B5): 259264.Google Scholar
Sellschop, J. P. F. 1987 Progress in accelerator mass spectrometry. In Gove, H. E., Litherland, A. E. and Elmore, D., eds., Proceedings of the 4rd International Symposium on Accelerator Mass Spectrometry. Nuclear Instruments and Methods in Physics Research B29: 439445.CrossRefGoogle Scholar
Slota, P. J. Jr., Jull, A. J. T., Linick, T. W. and Toolin, L. J. 1987 Preparation of small samples for 14C accelerator targets by catalytic reduction of CO. Radiocarbon 29(2): 303306.CrossRefGoogle Scholar
Slota, P. J. and Taylor, R. E. 1989 AMS 14C analysis of samples from archaeological contexts: Pretreatment and target preparation. In Ericson, J. E. and Taylor, R. E., eds., University of California Accelerator Mass Spectrometry I, Proceedings of the First U.C. Conference on AMS . Institute of Geophysical and Planetary Physics, University of California, Lawrence Liver-more National Laboratory. CONF–8602126: 3043.Google Scholar
Taylor, B. N. and Kuyatt, C. E. 1994 Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results . NIST Technical Note 1297. Washington, D.C., U.S. Government Printing Office: 20 p.Google Scholar
Verkouteren, R. M., Klouda, G. A., Currie, L. A., Donahue, D. J., Jull, A. J. T. and Linick, T. W. 1987 Preparation of microgram samples on iron wool for radiocarbon analysis via accelerator mass spectrometry: A closed-system approach. In Gove, H. E., Litherland, A. E. and Elmore, D., eds., Proceedings of the 4th International Symposium on Accelerator Mass Spectrometry. Nuclear Instruments and Methods in Physics Research B29: 4144.Google Scholar
Verkouteren, R. M. and Klouda, G. A. 1992 Factorial design techniques applied to optimization of AMS graphite target preparation. In Long, A. and Kra, R. S., eds., Proceedings of the 14th International 14C Conference. Radiocarbon 34(3): 335343.Google Scholar
Vogel, J. S. 1992 Rapid production of graphite without contamination for biomedical AMS. In Long, A. and Kra, R. S., eds., Proceedings of the 14th International 14C Conference. Radiocarbon 34(3): 344350.Google Scholar
Vogel, J. S. 1995 Report of the AMS sample preparation workshop, Saturday 13 August 1994. In Cook, G. T., Harkness, D. D., Miller, B. F. and Scott, E. M., eds., Proceedings of the 15th International 14C Conference. Radiocarbon 37(2): 815817.Google Scholar
Vogel, J. S., Nelson, D. E. and Southon, J. R. 1987 Contamination of small carbon samples during graphite preparation by catalytic reduction. In Hedges, R. E. M. and Hall, E. T., eds., Workshop on Techniques in Accelerator Mass Spectrometry . Oxford, ORAU: 813.Google Scholar
Vogel, J. S., Southon, J. R., Nelson, D. E. and Brown, T. A. 1984 Performance of catalytically condensed carbon for use in accelerator mass spectrometry. In Wölfli, W., Polach, H. A. and Anderson, H. H., eds., Proceedings of the 3rd International Symposium on Accelerator Mass Spectrometry. Nuclear Instruments and Methods in Physics Research 233 (B5): 289293.Google Scholar
Wilson, A. T. 1992 A simple technique for converting CO2 to AMS target graphite. In Long, A. and Kra, R. S., eds., Proceedings of the 14th International 14C Conference. Radiocarbon 34(3): 318320.Google Scholar