This method is for determining trace methyl acetylene and propadiene (MAPD) in high purity polymer grade propylene liquid or gas using a preconfigured, commercially available gas chromatograph. Other impurities of C3-C5 if present can also be determined. The range of quantitation for each component is 0.2 to 2000 mass- (or mol-) ppm. This method can be used to determine trace impurities in ethylene with appropriate gas injection valve and customized run program. For a full characterization of the C5 minus impurities to a lower limit of quantitation of 2 ppm refer to UOP 899.