A gas chromatography (GC) method for the determination of alkenes in complex hydrocarbon mixtures containing aromatic and saturated hydrocarbons is presented. The method enables selective and quantitative bromination of alkenes without affecting aromatic and saturated compounds. The dibromoalkanes formed are detected with minimal interference from coeluting hydrocarbons by bromine-selective atomic emission detection, with sub-nanogram bromine sensitivity. The method is applied to alkenes in gasolines, wherein those having lower octane number contain higher amounts of alkenes and those with higher octane number contain relatively lower levels. This method has potential for further refinement for all;ene analysis in different types of hydrocarbon samples. (C) 1999 Elsevier Science B.V. All rights reserved.