This method is for determining C₅ and lighter diolefins, mono-olefins, and paraffins in olefinic naphthas. Resolved acetylenes, and resolved C₆ hydrocarbons, including resolved dienes, are also identified. The method is applicable to selective hydrogenation process feeds, products, and other process streams with similar matrixes having a final boiling point of 260° or lower. Components that do not elute from the chromatographic system under the specified conditions are not determined. The lower limit of detection for any compound is 0.01 mass %.