ASTM D6866 and radiocarbon analysis

Carbon-14 (or radiocarbon) analysis is widely used in our laboratory analysis and is also used for research and analysis of bio-based products.

WHAT IS ASTM D6866?

ASTM D6866 is a test method developed by ASTM International. This protocol describes precisely how to experimentally measure the biobased carbon content of solid, liquid and gaseous samples using radiocarbon (also known as Carbon-14) analysis.  

Radiocarbon analysis for industry

Raw materials or products from your suppliers, radiocarbon analysis is mainly used for industrialists.

CIRAM laboratories analyse the content of bio-based products in materials at each stage. We evaluate products in R&D, under development, as well as finished products, ready to be marketed. Measuring the carbon-14 in your products allows you to define the quantity and proportion of bio-based and petro-based materials.

Radiocarbon analysis to measure the content of bio-based products

It is important to differentiate between two types of carbon:

• Modern carbon: the current biomass (cereals, oils, algae, organic waste) used to manufacture biobased molecules contains exclusively so-called "modern" carbon;
• Ancient carbon: oil used to manufacture synthetic products contains only 'ancient' carbon.

By measuring the ratio of 14C, 13C and 12C isotopes, radiocarbon analysis makes it possible to quantify the proportion of modern (i.e. biobased) and old (petroleum-based) carbon present in a product.

Please note that in order to comply with ASTM D6866, the sample must first be transformed into pure carbon (graphite) because it is this graphite target that will be analysed in the laboratory by a particle accelerator coupled to a mass spectrometer (AMS).

According to the international standard ASTM 6866, it is possible to measure the carbon-14 content by three different methods, but only the AMS technique will be discussed here.

Measurements according to ASTM D6866

In order to comply with the regulations in force and ASTM D6866, the biogenic carbon content must be expressed as a percentage of modern carbon in relation to the total carbon for a result expressed in pMC (Percentage of Modern Carbon).

The reference value, called REF, corresponds to 100% biobased carbon at a given date.

It should be noted that in 2022, still according to the ASTM D6866 standard, the REF was 100 pMC for a 100% biosourced carbon content, whereas the value was 102 pMC in 2015 and 200 in 1962. In order to harmonise the results and keep the same reference values, it is considered that over the last four years, 100 pMC represents 100% biobased carbon content in relation to total carbon.

The ASTM D6866 standard also allows for a possible variation of ±3% of the biobased carbon content with the radiocarbon technique. This margin of error considers, for example, a measurement of 97 pMC as 100% biobased carbon to total carbon.

Measuring materials containing inorganic carbonates

For materials containing inorganic carbonates, ASTM D6866 indicates that chemical etching can be performed to remove the carbonates. As carbonates contain carbon from geological materials, there is a risk that the pMC value will be artificially reduced and the results will be distorted. This is because the radiocarbon method considers the carbon in geological carbonates and the carbon in oil in the same way. This precision is important because, unlike the EN 16640 standard which considers the percentage of biobased carbon in relation to total carbon, the international standard ASTM D6866 determines the biobased carbon content in relation to total organic carbon.

CIRAM, SPECIALISTS IN RADIOCARBON ANALYSIS

As specialists in radiocarbon analysis, our scientists carry out all tests in the laboratory. We comply with international standards in order to deliver accurate results thanks to innovative solutions and meticulous support.