New primary reference materials for gas composition for carbon capture, utilisation and storage and how they support industry and meet the technical specifications of European manufacturers

<ns3:p> This work describes the development and validation of new Primary Reference Materials (PRMs) for trace impurities in carbon dioxide (CO <ns3:sub>2</ns3:sub> ), addressing a key metrological gap for carbon capture, utilisation, and storage (CCUS) applications. CO <ns3:sub>2</ns3:sub> streams captured from industrial sources inevitably contain impurities such as water, sulfur oxides, nitrogen oxides, hydrogen, and hydrocarbons. Accurate and traceable quantification of these species is essential to protect transport infrastructure, ensure compliance with project specifications, and enable safe long-term geological storage. International and project-specific guidelines, including ISO/TR 27913, Porthos, and Northern Lights, define stringent impurity limits, underscoring the need for reliable gas standards for calibration and validation of analytical instruments. Binary and multi-component PRMs were prepared by VSL, NPL, CMI, IPQ, and SINTEF ER using ISO 6142-1 gravimetric methods. The mixtures covered sulfur dioxide, hydrogen sulfide, nitrogen dioxide, nitrous oxide, water, dimethyl sulfide, ethanol, and non-condensable gases (N <ns3:sub>2</ns3:sub> , Ar, H <ns3:sub>2</ns3:sub> , O <ns3:sub>2</ns3:sub> , CH <ns3:sub>4</ns3:sub> , and CO) at amount fractions relevant to CCUS specifications. In parallel, dynamic preparation systems and a portable trace gas generator were validated as alternative approaches for producing low-level mixtures of reactive species such as ammonia. PRM stability was investigated over a two-year period. Sulfur dioxide, hydrogen sulfide, dimethyl sulfide, ethanol, and nitrous oxide demonstrated stability within their expanded uncertainties. In contrast, sulfur dioxide, nitrogen dioxide, and nitric oxide in multi-component mixtures exhibited significant degradation, indicating pronounced reactivity and wall effects. Dynamic dilution systems developed by VSL and NPL produced mixtures consistent with static PRMs within 1–5%, while the portable trace gas generator achieved ammonia generation in CO <ns3:sub>2</ns3:sub> with a relative uncertainty of approximately 2%. These results establish a robust metrological basis for impurity analysis in CO <ns3:sub>2</ns3:sub> . The PRMs developed within MetCCUS provide traceable calibration capabilities aligned with European CO <ns3:sub>2</ns3:sub> quality specifications, supporting reliable monitoring and safe operation of CCUS infrastructure. </ns3:p>