Analytical assurance of hydrogen purity: A comprehensive framework for trace contaminant verification and conformity assessment

• Hydrogen purity assurance reviewed across the full production-to-dispensing chain. • Multi-detector GC, MS, and IR spectroscopy compared for sub-ppm contaminant detection. • Framework integrates sampling, calibration, and matrix-matched validation. • Guard-banding and uncertainty governance formalized for conformity decisions. • Proposes fit-for-purpose quality model with traceable, auditable verification tools. The precise identification of trace contaminants in hydrogen is essential for safeguarding proton-exchange membrane fuel cells (PEMFCs), facilitating reliable fuel cell implementation, and advancing global energy transition objectives outlined in Sustainable Development Goal (SDG)-7, which pertains to affordable and clean energy. This review synthesizes the analytical, metrological, and operational specifications necessary for the quantification of impurities at parts-per-million (ppm) to parts-per-billion (ppb) concentrations throughout the hydrogen production, storage, transportation, and dispensing processes that are vital for achieving SDG-9 (industry, innovation, and infrastructure) and SDG-13 (climate action). Comparative evaluations of the performance of multi-detector gas chromatography (GC), laser-based spectroscopy (CRDS/FTIR), and mass-spectrometric techniques are provided, with a focus on matrix-matched calibration, interference suppression, recovery verification, and the stability of reactive species such as sulfur compounds, carbonyls, and ammonia. The review further delineates a metrologically rigorous conformity-assessment framework that incorporates integrity of sampling systems, memory mitigation strategies, preconcentration methodologies, SI-traceable calibration, uncertainty quantification, and guard-banded decision protocols to ensure robust compliance with ISO 14687 and SAE J2719. Instead of merely reiterating numerical thresholds, the framework associates instrument capability with distinct uncertainty-aware decision protocols, thereby facilitating trustworthy quality assurance at the boundaries of specifications. Practical recommendations are offered for online and near-line monitoring systems, verification intervals, and standardized operating procedures (SOPs) to promote reproducible, auditable hydrogen quality assurance within the context of emerging clean energy infrastructures aligned with SDG objectives.