This method is for determining individual trace C5 minus hydrocarbon impurities in hydrogen or liquefied petroleum gas (LPG), where the specific trace components are sufficiently resolved from the major components, typically propane/propylene or ethane/ethylene. Components eluting after ethyl acetylene are grouped and reported as heavies. The range of quantitation for each component is 2 to 3000 mol-ppm, however, the lower limit of quantitation increases when major components interfere with the resolution of the impurities.