This method is for determining individual components in C₂ through C₅ gaseous hydrocarbon mixtures. Most olefins including 1-butene and isobutylene are separated, although some are not sufficiently resolved for individual determination. The lower limit of detection for a single component is 0.05 mol-%. C₆ and heavier components, if present, may not elute quantitatively from the system or may interfere with present or subsequent analyses.