ASTM D6866-10

Presidential (Executive) Orders 13101, 13123, 13134, Public Laws (106-224), AG ACT 2003 and other Legislative Actions all require Federal Agencies to develop procedures to identify, encourage and produce products derived from biobased, renewable, sustainable and low environmental impact resources so as to promote the Market Development Infrastructure necessary to induce greater use of such resources in commercial, non food, products. Section 1501 of the Energy Policy Act of 2005 (Public Law 109–58) and EPA 40 CFR Part 80 (Regulation of Fuels and Fuel Additives: Renewable Fuel Standard Requirements for 2006) require petroleum distributors to add renewable ethanol to domestically sold gasoline to promote the nation's growing renewable economy, with requirements to identify and trace origin.

Method A utilizes Liquid Scintillation Counting (LSC) radiocarbon (¹⁴C) techniques to quantify the biobased content of a given product with maximum total error of 15 % count, which is associated with sample preparation and actual counting. This test method is based on LSC analysis of CO₂ cocktails after collecting the CO₂ in a suitable absorbing solution.

Method B utilizes Accelerator Mass Spectrometry (AMS) and Isotope Ratio Mass Spectrometry (IRMS) techniques to quantify the biobased content of a given product with possible uncertainties of 1 to 2 % and 0.1 to 0.5 %, respectively. Sample preparation methods are identical to Method A, 8.2–8.5. Method B diverges after 8.5 and rather than LSC analysis the sample CO₂ remains within the vacuum manifold and is distilled, quantified in a calibrated volume, transferred to a quartz tube, torch sealed. Details are given in 12.7-12.10. The stored CO₂ is then delivered to an AMS facility for final processing and analysis.

Method C uses LSC techniques to quantify the biobased content of a product. However, whereas Method A uses LSC analysis of CO₂ cocktails, Method C uses LSC analysis of sample carbon that has been converted to benzene. This test method determines the biobased content of a sample with a maximum total error of ±3 % (absolute).

Although Methods A and C are less sensitive than that of using AMS/IRMS, they have two distinct advantages: (1) lower costs per evaluation, and (2) much higher instrument availability worldwide. Indeed, LSC is the most widely used measurement for ¹⁴C determination. Method B is commonly used when the authenticity of the LSC radiocarbon results are in dispute, when sample size is greatly restricted or costly per mass of sample, or when the carbon content of the sample is less than 10 % by weight.

The test methods described here directly discriminate between product carbon resulting from contemporary carbon input and that derived from fossil-based input. A measurement of a product’s ¹⁴C/¹²C content is determined relative to the modern carbon-based oxalic acid radiocarbon Standard Reference Material (SRM) 4990c, (referred to as HOxII). It is compositionally related directly to the original oxalic acid radiocarbon standard SRM 4990b (referred to as HOxI), and is denoted in terms of f_M, that is, the sample’s fraction of modern carbon. (See Terminology, Section 3.)

Reference standards, available to all laboratories practicing these test methods, must be used properly in order that traceability to the primary carbon isotope standards are established, and that stated uncertainties are valid. The primary standards are SRM 4990c (oxalic acid) for ¹⁴C and RM 8544 (NBS 19 calcite) for ¹³C. These materials are available for distribution in North America from The National Institute of Standards and Technology (NIST), and outside North America from the International Atomic Energy Agency (IAEA), Vienna, Austria.

Acceptable SI unit deviations (tolerance) for the practice of these test methods is ±5 % from the stated instructions unless otherwise noted.