Ready biodegradability: Headspace test according to OECD 310
This screening method (OECD 310, CO2 in sealed vessels/headspace test) determines ready biodegradability by measuring aerobic CO2 mineralisation and expressing the extent of biodegradation as a percentage of the theoretical maximum inorganic carbon (ThIC). It is applicable to a wide range of chemical substances, including water‑soluble and water‑insoluble materials, poorly soluble compounds, and strongly adsorbing substances. It can also be adapted to volatile compounds through appropriate headspace-to-liquid ratios and handling.
The test can be used to assess the ultimate biodegradability of surfactants in detergents under Regulation (EC) No 648/2004. EN ISO 14593:1999 (the CO2 headspace test) is referenced in the regulation, and OECD 310 is the technically equivalent OECD guideline. Surfactants are considered readily biodegradable if they achieve ≥60% mineralisation within 28 days. The same pass criterion also applies under the REACH microplastics restriction (Commission Regulation (EU) 2023/2055), which explicitly lists OECD 310 as an accepted biodegradability test method.
In the test, samples are incubated in sealed bottles with an air headspace to supply oxygen for aerobic degradation, and CO2 evolved during incubation is quantified as inorganic carbon (IC) against blank controls at scheduled sampling times.
Two principal measurement approaches are described: headspace gas can be acidified to pH <3 and analyzed for IC, with results recorded as mg C/L, or the liquid phase can be treated with NaOH to absorb CO2 and then injected to the IC analyzer. For water‑soluble substances, an optional supporting endpoint measures primary biodegradation via DOC removal, determined on filtered liquid using a DOC analyzer.
Reported outputs are the percent biodegradation expressed as % of ThIC (calculated from IC recovered in liquid plus headspace versus blanks), the intermediate IC concentrations from the analyzer in mg C/L, and, where performed, DOC removal values from the DOC analyzer.
- Suitable sample matrices
- Polymers, chemicals
- Available quality systems
- Accredited testing laboratory
- Standard
- Method expert
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