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We present a low-cost, high-throughput method for converting many types of organic samples into graphite. The method combines sample combustion and graphitization in a single process. Using a modified sealed graphitization method, samples are placed in a Pyrex tube containing zinc, titanium hydride and iron catalyst. The tube is evacuated, flamed sealed, and placed in a muffle furnace for 7 hours. Graphite forms on the iron and is then analyzed for 14C content using either of NOSAMS’s two AMS systems. This method has been shown to work on a variety of organic samples including pure compounds, wood, peat, collagen and humics. This simplified procedure could be especially useful in reconnaissance studies in which it is desired to rapidly measure a large number of samples (untreated or pretreated), at low-cost with analytical precision and accuracy approaching that of traditional hydrogen reduction methods.

The development of robust sample preparation techniques for ocean science research has been a hallmark of NOSAMS since its inception. Improvements to our standard methods include reducing the minimum size of the samples we can analyze, building modular graphite reactors of different sizes that we can swap in and out depending on our sample stream, and modifying our carbonate acidification methods to improve handling of the smaller samples we now receive. A relatively new instrument, the Ramped PyrOx, which allows the separation of organic matter into thermal fractions, has attracted much interest as a research and development tool. We will also discuss our progress on incorporating a Picarro isotope analyzer into our sample preparation options.

The development of robust sample preparation techniques for ocean science research has been a hallmark of NOSAMS since its inception. Improvements to our standard methods include reducing the minimum size of the samples we can analyze, building modular graphite reactors of different sizes that we can swap in and out depending on our sample stream, and modifying our carbonate acidification methods to improve handling of the smaller samples we now receive. A relatively new instrument, the Ramped PyrOx, which allows the separation of organic matter into thermal fractions, has attracted much interest as a research and development tool. We will also discuss our progress on incorporating a Picarro isotope analyzer into our sample preparation options.

We present a low-cost, high-throughput method for converting many types of organic samples into graphite. The method combines sample combustion and graphitization in a single process. Using a modified sealed graphitization method, samples are placed in a Pyrex tube containing zinc, titanium hydride and iron catalyst. The tube is evacuated, flamed sealed, and placed in a muffle furnace for 7 hours. Graphite forms on the iron and is then analyzed for 14C content using either of NOSAMS’s two AMS systems. This method has been shown to work on a variety of organic samples including pure compounds, wood, peat, collagen and humics. This simplified procedure could be especially useful in reconnaissance studies in which it is desired to rapidly measure a large number of samples (untreated or pretreated), at low-cost with analytical precision and accuracy approaching that of traditional hydrogen reduction methods.

© The Arizona Board of Regents on behalf of the University of Arizona, 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Radiocarbon 57, no. 1 (2015): 109–122, doi:10.2458/azu_rc.57.18118., In response to the increasing demand for 14C analysis of samples containing less than 25 µg C, ultra-small graphitization reactors with an internal volume of ~0.8 mL were developed at NOSAMS. For samples containing 6 to 25 µg C, these reactors convert CO2 to graphitic carbon in approximately 30 min. Although we continue to refine reaction conditions to improve yield, the reactors produce graphite targets that are successfully measured by AMS. Graphite targets produced with the ultra-small reactors are measured by using the Cs sputter source on the CFAMS instrument at NOSAMS where beam current was proportional to sample mass. We investigated the contribution of blank carbon from the ultra-small reactors and estimate it to be 0.3 ± 0.1 µg C with an Fm value of 0.43 ± 0.3. We also describe equations for blank correction and propagation of error associated with this correction. With a few exceptions for samples in the range of 6 to 7 µg C, we show that corrected Fm values agree with expected Fm values within uncertainty for samples containing 6–100 µg C., This work was funded by the NSF Cooperative Agreement for the Operation of a National Ocean Sciences Accelerator Mass Spectrometry Facility (OCE-0753487). S R Shah Walter was also partially supported by the WHOI Postdoctoral Scholar Program.