Review of analytical methods for ISO 14687:2025 Grade F hydrogen quality assessment for internal combustion engine applications

The growing urgency to mitigate climate change and the progressive depletion of fossil-derived feedstocks have intensified interest in hydrogen-fuelled internal combustion engines (H₂-ICEs) as a low-carbon propulsion technology. Fuel quality is a critical factor influencing combustion behaviour, durability, emissions, and after-treatment compatibility. The recently published ISO 14687:2025 standard introduces Grade F-1 and F-2 hydrogen specifications for vehicular and stationary H₂-ICE applications, respectively. This review critically evaluates state of the art analytical methodologies for quantifying Grade F impurities, including N 2 , O 2 , Ar, H₂O, CH₄, non-methane hydrocarbons, CO₂, CO, total sulphur species, NH₃, and particulate matter. Emphasis is placed on the metrological traceability, sensitivity, selectivity and overall analytical performance. Techniques assessed include gas chromatography (GC-TCD, GC-FID with and without methaniser, GC-PDHID, GC–MS, and GC-SCD/FPD), high-sensitivity optical spectroscopy (CRDS, FTIR, Raman spectroscopy, and OFCEAS), ammonia determination by ion chromatography methods, and gravimetric and optical approaches for particulate analysis. The analytical techniques are compared with respect to detection limits (sub-μmol/mol to nmol/mol range), linear dynamic range, matrix effects, cross-sensitivity, and operational robustness under real-world sampling conditions. Their capability to meet ISO 14687:2025 Grade F impurity thresholds is assessed, together with their suitability for laboratory-based analysis and online monitoring applications. Comparison with ISO 14687 Grade D (fuel cell grade) hydrogen highlights the reduced analytical requirements of Grade F. Because H₂-ICEs are less sensitive than PEM fuel cells to many ultra-trace contaminants, industry can use simpler, cheaper and more widely available analytical solutions, e.g. GC-TCD, GC-FID/methaniser-FID and selected optical methods. The principal analytical challenges remain representative sampling and trace-level measurement of sulphur species, ammonia, water, and particulate matter. Overall, the reduced impurity scope and less stringent limits of Grade F enable the use of simpler, more cost-effective analytical strategies than Grade D, providing laboratories and industry with a practical framework for routine hydrogen quality assurance in H₂-ICE applications.