This method is for determining diolefins in FCC derived C5olefinic streams by gas chromatography (GC). The individualdiolefins cannot be separated and individually identified, but areeluted and calculated as a composite. 3-Methyl-1,2-butadiene is notdetermined by this method. 1,2-Pentadiene and 2,3-pentadiene arenot expected to be present in C5 streams and it is not known ifthey can be determined by this method. The lower determinationlimit is 10 mass-ppm.