This method is for determining trace levels of select oxygenated hydrocarbons, with boiling points up to 138C, in refinery gas streams, C4 liquefied petroleum gas (LPG), light isomerate and naphtha. Mono-oxygenated hydrocarbons determined include C1 through C5 alcohols, and C2 through C6 carbonyls and ethers. Formaldehyde, if present, is not determined by this method. Di-oxygenated hydrocarbons determined include C2 through C4 methyl esters and 1,4-dioxane. The range of quantitation for each individual oxygenate in liquid streams is 0.2 to 250 mass-ppm (mg/kg) and in gas/LPG streams is 1.0 to 250 mass-ppm (mg/kg). Inorganic compounds containing oxygen, such as water, carbon monoxide, carbon dioxide or heteroatoms such as nitrogen, chlorine or sulfur are not determined. Unsaturated oxygenated hydrocarbons may be detected but are not identified. Certain oxygenated hydrocarbons are not separated and are reported as composites. Some sulfur and nitrogen compounds are known to elute in the oxygenate region of the chromatogram.